Methods and structure for recovery of write fault errors in a dynamically mapped mass storage device

ABSTRACT

Methods and structures for recovering from an off-track position error in a dynamically mapped storage device. In a dynamically mapped storage device data is dynamically mapped to a physical location on the recordable media. Thus, when a write fault occurs, such as an off-track position error, the data may be re-written and re-mapped at a different location on the recordable media. In a dynamically mapped storage device data may be reordered into a sequential stream of contiguous physical data blocks. Random host data blocks may be mapped into sequential physical data blocks on the recordable media. Further, the sequential reordering of the data blocks may ensure that no data is present in tracks or sectors directly ahead of the track of sector being written. Further, the system has the ability to store multiple revolutions of host supplied data within the disk drive memory buffer and maintain the information in memory while writing it to the recordable media. The multiple revolutions of host supplied data may be used to recover from the destruction of previously written physical blocks overwritten during an off-track position error.

RELATED APPLICATIONS

This patent application claims priority as a continuation-in-part ofcommonly owned, co-pending U.S. patent application Ser. No. 11/122,751filed 5 May 2005 and entitled: Methods and Structure for DynamicallyMapped Mass Storage Device which is hereby incorporated by reference(also referred to herein as the “parent patent application” or simplythe “Parent”). This patent application is also related to and claimspriority to the following United States Provisional Patent Applications:Ser. No. 60/728,899 filed 21 Oct. 2005 and entitled: Dynamic MultipleIndirection of Logical to Physical Space within a Disk Drive, Ser. No.60/728,904 filed 21 Oct. 2005 and entitled: LBA Indirect Dynamic DataDensity, Ser. No. 60/728,900 filed 21 Oct. 2005 and entitled: LBAIndirect On-the-Fly Head Depopulation, Ser. No. 60/728,898 filed 21 Oct.2005 and entitled: LBA Indirect Field Flawscan, Ser. No. 60/728,903filed 21 Oct. 2005 and entitled: LBA Indirect Appended Metadata StorageWhen Space Available, Ser. No. 60/728,902 filed 21 Oct. 2005 andentitled: LBA Indirect Disk Drive Write Fault System, Ser. No.60/729,377 filed 21 Oct. 2005 and entitled: Lead-in Writes in a DiskDrive for Thermal Stability, Ser. No. 60/728,897 filed 21 Oct. 2005 andentitled: Grown Defects without Performance Loss in an Indicated DiskDrive, all of which are commonly owned and hereby incorporated byreference. This patent application is also related to the followingcommonly owned and co-pending U.S. patent applications: Ser. No.11/583,533 filed 19 Oct. 2006 and entitled: METHODS AND STRUCTURE FORHANDLING GROWN DEFECTS INA DYNAMICALLY MAPPED MASS STORAGE DEVICE, Ser.No. 11/583,331 filed 19 Oct. 2006 and entitled: METHODS AND STRUCTUREFOR DYNAMIC DATA DENSITY INA DYNAMICALLY MAPPED MASS STORAGE DEVICE,Ser. No. 11/583,341 filed 19 Oct. 2006 and entitled: METHODS ANDSTRUCTURE FOR DYNAMIC APPENDED METADATA INA DYNAMICALLY MAPPED MASSSTORAGE DEVICE, Ser. No. 11/583,550 filed 19 Oct. 2006 and entitled:METHODS AND STRUCTURE FOR ON-THE-FLY HEAD DEPOPULATION INA DYNAMICALLYMAPPED MASS STORAGE DEVICE, Ser. No. 11/583,623 nun filed 19 Oct. 2006and entitled: METHODS AND STRUCTURE FOR DYNAMIC MULTIPLE INDIRECTIONSINA DYNAMICALLY MAPPED MASS STORAGE DEVICE, Ser. No. 11/583,767 filed 19Oct. 2006 and entitled: METHODS AND STRUCTURE FOR FIELD FLAWSCAN IN ADYNAMICALLY MAPPED MASS STORAGE DEVICE, and Ser. No. 11/583,502 a filed19 Oct. 2006 and entitled: METHODS AND STRUCTURE FOR WRITING LEAD-INSEQUENCES FOR HEAD STABILITY INA DYNAMICALLY MAPPED MASS STORAGE DEVICEwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to mass storage device controlstructures and methods in a dynamically mapped mass storage device andmore specifically to structures and methods within the controller of adynamically mapped mass storage device, such as a disk drive, operableto recover from write fault errors of the dynamically mapped storagedevice.

2. Discussion of Related Art

A common example of a mass storage device is a disk drive having one ormore rotating recordable media surfaces each with a correspondingread/write head for writing information thereon and for reading backpreviously written information. As used herein, “disk drive” is intendedto represent such devices with rotating storage media and correspondingread/write heads as well as other similar, exemplary mass storagedevices. Further, “recordable media”, “recordable media surface” and“persistent media” are all intended as synonymous and represent one ormore media surfaces on which information may be recorded and read backtypically using optical or magnetic encoding and modulation techniquesand structures.

It is generally known in the disk drive arts that fixed sized units ofdata are physically stored about the circumference of concentric trackslaid out on a magnetic or optical persistent storage media. These fixedsize units of data are often referred to as “blocks” or “sectors”. Aparticular block or sector physically located on the rotating storagemedia may be identified by its cylinder or track number and its sectoror block number within that track. In addition, where a disk driveincludes multiple storage media services each with an independent R/Whead, a particular head or surface number may identify the surface onwhich a particular physical block or sector is located. Such physicaladdresses are often referred to as “CHS” (an acronym for cylinder, head,and sector).

Most present-day disk drives permit a logical block address to beutilized by the host system or device rather than a specific CHSdesignation to identify a particular block or sector to be accessed.Such a logical address is typically a sequential range of logical blocknumbers from zero through N where N is the maximum number of physicalsectors or blocks available on the disk drive storage media. The hostmay therefore address or identify a particular physical block by itslogical block address (“LBA”) rather than by the more complex andcumbersome CHS designation. The disk drive (specifically a disk drivecontroller component of the disk drive) then translates or maps aprovided logical block address (LBA) into a corresponding physicallocation (typically, a CHS address designation). Further, such logicaladdressing permits the disk drive controller to transparently redirectaccess for a particular physical block to an alternate or spare physicalblock where the original physical block has been damaged or is otherwiseinaccessible. The disk drive controller merely translates the suppliedLBA to a different physical block of the disk storage media.

As presently practiced in the art, physical sectors or blocks on thedisk drive are all the same size as measured in number of bytes. Forexample, present disk drives often utilize a block or sector size ofeither 512 or 1024 bytes. The particular physical block or sector sizemay be any suitable size selected for a particular disk driveapplication in accordance with performance and storage capacity designchoice tradeoffs. However, as presently known in the art, physicalsectors on a disk drive are all a common, designated size. The logicalblocks utilized by a host device in addressing storage of the disk driveare also a fixed size. Though the fixed size of a logical block may bedifferent than the fixed size of the physical disk blocks, as presentlypracticed a simple arithmetic computation may be used because thephysical block size and logical block size are typically integralmultiples/fractions of one another. In other words, as presentlypracticed, a logical block size is typically an integral multiple of thephysical block or sector size. Such a strict arithmetic relationshipbetween the logical block size and physical block size precludes anumber of possible features and enhancements within a disk drive.

The Parent discloses methods and structures for a dynamically mappedstorage device in which mapping structures and methods hide the userfrom any knowledge of the actual location of user supplied data bydynamically mapping user supplied logical blocks to physical disk blockswherein the size of a user supplied logical block is independent of thesize of the one or more corresponding physical disk blocks used to storethe user supplied logical block. Typically the logical block size isfixed while the physical disk block size may vary since the mapping iscompletely localized within the storage device.

Thus the Parent provides improved logical to physical mapping for blocksof data within a disk drive of such that the logical block size definedby an attached host system may be independent of the physical block sizeused within the disk drive for storage of information.

As a disk drive writes data to the recordable media, write fault errorsmay occur in instances where data is not correctly written to disk. Inpresent disk drives, when the write head deviates too far from the trackcenter, the write process is aborted and the write head attempts tore-write the data to the same physical location on subsequentrevolutions. If the data is written too far from the center of thetrack, it may be unreadable during subsequent read processes. There-writing process requires a minimum of one revolution of time, whichimpacts the performance of the disk drive. In some cases where the writehead deviates too far from the track center data on adjacent trackswritten earlier in time may be overwritten and destroyed. Since theadjacent track is likely not saved in cache memory of the disk drive andmay no longer be capable of being read, the overwritten data may not berecoverable.

It remains an ongoing problem in all storage devices to minimize oreliminate the effects of off-track position errors. Since present daydisk drives are likely to receive a random sequence of write requestsfrom an attached host located at various logical block addresses andpositions on the disk drive, an off-track position error may likelydestroy data that was not recently written by the disk drive. Thus, thedata may be unrecoverable. Further, off-track position errors result insignificant performance losses of the disk drive. To minimize off-trackposition errors, position sampling equipment with high sampling ratesare often used to determine immediately whether the write head isoff-track. This adds complexity to the disk drive, as well as requiringadditional space on the recordable media for the servo synchronizationinformation used for sampling, reducing the overall capacity of the diskdrive.

SUMMARY OF THE INVENTION

The present invention solves the above and other problems, therebyadvancing the state of the useful arts, by providing methods andstructures for recovery from write fault errors in a dynamically mappedstorage device. In a dynamically mapped storage device data isdynamically mapped to a physical location on the recordable media. Thus,when a write fault error occurs, such as an off-track position error,the data may be re-written and re-mapped at a different location on therecordable media. In a dynamically mapped storage device data may bereordered into a sequential stream of contiguous physical data blocks.Random host data blocks may be mapped into sequential physical datablocks on the recordable media. Further, the sequential reordering ofthe data blocks may ensure that no data is present in tracks or sectorsdirectly ahead of the track or sector being written. Further, the systemhas the ability to store multiple revolutions of host supplied datawithin the disk drive memory and maintain the information in memorywhile writing data to the disk. If the write head deviates too far fromthe track center the data that was written incorrectly may be remapped,as well as any adjacent data that may have been destroyed due toencroachment. Therefore, the disk drive may recover from a largeposition error “after the fact”.

On embodiment of the invention is a method operable in association witha dynamically mapped storage device. The method comprises: detecting anoff-track position error condition while writing a supplied logicalblock at a first physical block address of a recordable media of thedynamically mapped storage device; re-writing the supplied logical blockat a second physical block address of the recordable media responsive todetecting the off-track position error; and adjusting a mapping table ofthe dynamically mapped storage device to map the supplied logical blockat the second physical block address.

Another embodiment of the invention is a method operable in associationwith a dynamically mapped storage device. The method comprises:receiving a supplied logical block to be written to a recordable mediaof the dynamically mapped storage device; adding the supplied logicalblock to a buffer including data to be written to the recordable media;writing the supplied logical block at a first physical block address ofthe recordable media of the dynamically mapped storage device; detectingan off-track position error condition while writing the supplied logicalblock; and recovering from the off-track position error and re-writingthe supplied logical block at a second physical block address of therecordable media.

Another embodiment of the invention is a dynamically mapped storagedevice adapted to receive a request from an attached host for access toa logical block identified by a logical block address. The dynamicallymapped storage device comprises: a recordable media comprising aplurality of physical disk blocks identified by a corresponding physicaldisk block address; and a disk controller adapted to detect an off-trackposition error condition while writing a supplied logical block at afirst physical block address of the recordable media, and furtheradapted to re-write the supplied logical block at a second physicalblock address of the recordable media responsive to detecting theoff-track position error; and further adapted to adjust the mappingtable to map the supplied logical block at the second physical blockaddress.

BRIEF DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element or same type ofelement on all drawings.

FIG. 1 is a block diagram of an exemplary disk drive enhanced inaccordance with features and aspects hereof to provide indirect logicalto physical mapping and to thereby enable numerous related enhancementsfor capacity, performance, and reliability.

FIG. 2 is a block diagram depicting an exemplary logical to physicalmapping element in accordance with features and aspects hereof to mapsample logical block addresses into corresponding physical disk blockaddresses.

FIG. 3 is a schematic diagram suggestive of the variable physical diskblock sizes that may be disposed at different radial track positions ofa disk media surface in accordance with features and aspects hereof.

FIG. 4 is a diagram describing an exemplary mapping of logical blockaddresses to corresponding physical disk block addresses in accordancewith exemplary data structures embodying features and aspects hereof.

FIG. 5 is a block diagram of an exemplary master table providing logicalto physical mapping structures associated with features and aspectshereof.

FIG. 6 is a block diagram providing additional details of exemplaryentries in the mapping tables of FIG. 5.

FIG. 7 is a block diagram suggesting utilization of the exemplarymapping table structures of FIG. 5 to translate or map exemplary logicalblock addresses into corresponding physical disk block addresses inaccordance with features and aspects hereof.

FIG. 8 is a block diagram of an exemplary data frame structure forstoring physical disk blocks and exemplary, associated metadata inaccordance with features and aspects hereof.

FIG. 9 is a block diagram suggesting an exemplary circulardefragmentation technique associated with features and aspects hereoffor defragmenting and coalescing physical disk blocks in accordance withfeatures and aspects hereof.

FIG. 10 is a flowchart describing exemplary high level processing of anI/O request received from an attached host device involving logical tophysical mapping in accordance with features and aspects hereof.

FIG. 11 is a flowchart providing additional exemplary details of I/Orequest processing involving logical to physical block address mappingin accordance with features and aspects hereof.

FIG. 12 is a flowchart providing further details of an exemplary methodfor mapping logical to physical addresses utilizing a particularexemplary mapping structure embodying features and aspects hereof.

FIG. 13 is a flowchart describing an exemplary background process forperiodic defragmentation of the physical storage space in accordancewith features and aspects hereof.

FIG. 14 is a block diagram of a disk drive controller providing indirectlogical to physical mapping in accordance with features and aspectshereof to thereby enable compression of data stored on, and retrievedfrom, the physical disk media.

FIGS. 15 through 18 are block diagrams suggesting the potential benefitsderived from data compression within a disk drive as in FIG. 14.

FIG. 19 is flowchart describing exemplary disk drive power upinitialization in accordance with mapping features and aspects hereof.

FIG. 20 is a schematic diagram of recorded, densely packed, adjacenttracks written in accordance with mapping features and aspects hereof.

FIG. 21 is a schematic diagram of a disk recording surface having aplurality of densely packed tracks grouped between guard bands to permitrecovery of earlier recorded tracks in accordance with mapping featuresand aspects hereof.

FIG. 22 is a schematic diagram of a disk recording surface having aplurality of tracks with multiple indirections (multiple copies) of ahost supplied logical block mapped to multiple physical locations inaccordance with mapping features and aspects hereof.

FIG. 23 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide management of multiplecopies of a host supplied logical block mapped to and stored in multiplephysical locations of the dynamically mapped storage device inaccordance with features and aspects hereof.

FIG. 24 shows flowcharts of two exemplary cooperating methods operableto manage multiple physical copies of host supplied logical data forwriting and reading of same on a mapped storage device in accordancewith features and aspects hereof.

FIG. 25 is a flowchart of an exemplary method to monitor aspects of thedynamically mapped storage device to determine if previously writtenduplicate copies of host supplied logical blocks need be removed fromthe storage device in accordance with features and aspects hereof.

FIGS. 26 through 28 are flowcharts providing exemplary additionaldetails of aspects of the methods of FIG. 24.

FIG. 29 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide management of dynamicrecording density in writing of data to a mapped storage device inaccordance with features and aspects hereof.

FIG. 30 is a schematic diagram of a disk recording surface having aplurality of tracks grouped in zones of varying density in accordancewith mapping features and aspects hereof.

FIG. 31 is a schematic diagram of recorded adjacent tracks written withvariable track density on a mapped storage device in accordance withfeatures and aspects hereof.

FIGS. 32 and 33 are block diagrams suggesting the structure of frameswritten to a mapped storage device with varying bit density inaccordance with features and aspects hereof.

FIGS. 34 and 35 are flowcharts describing methods for management ofdynamic density for recording of data on a mapped storage device inaccordance with features and aspects hereof.

FIG. 36 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide management of fieldflawscan in accordance with features and aspects hereof.

FIGS. 37 through 39 are flowcharts describing exemplary methods forfield flawscan in accordance with features and aspects hereof.

FIG. 40 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to generate and utilize appendedmetadata in accordance with features and aspects hereof.

FIG. 41 is a flowchart describing an exemplary method in accordance withfeatures and aspects hereof to process a write request received from anattached host system.

FIG. 42 is a flowchart describing an exemplary method operable withinthe dynamically mapped storage device to monitor the current capacitythreshold value and, when appropriate, to migrate previously recordeddata with appended metadata to new locations, re-recording the hostsupplied data devoid of appended metadata.

FIG. 43 is a flowchart describing another exemplary method similar tothat of FIG. 41 discussed above for processing of received writerequests with host supplied data.

FIG. 44 is a flowchart describing an exemplary method operable in thestorage device controller of a logically mapped storage device—toperform and “unwind” operation, in response to an appropriate request.

FIG. 45 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide handling of anoff-track position error encountered while writing user supplied data toa recordable media.

FIG. 46 illustrates an off-track position error in a direction in whichno encroachment of an adjacent track may occur.

FIG. 47 illustrates an off-track position error in a direction in whichencroachment of an adjacent track may occur.

FIG. 48 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for handlingoff-track position errors.

FIG. 49 is a flowchart providing exemplary additional details of theprocessing of FIG. 48.

FIG. 50 is a flowchart providing exemplary additional details of anotherembodiment of the processing of FIG. 48.

FIG. 51 is a flowchart providing exemplary additional details of theprocessing of FIG. 50.

FIG. 52 is a flowchart representing another exemplary method operablewithin a storage device controller (e.g., disk controller) inconjunction with the mapping features and aspects discussed herein abovefor handling off-track position errors.

FIG. 53 is a flowchart providing exemplary additional details of theprocessing of FIG. 52.

FIG. 54 is a flowchart providing example additional details of theprocessing of FIG. 52.

FIGS. 55-58 are block diagrams depicting an exemplary buffer used by adisk controller.

FIG. 59 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to perform on-the-fly headdepopulation.

FIG. 60 is a schematic diagram of an exemplary disk drive includingmultiple recording surfaces.

FIG. 61 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for performingon-the-fly head depopulation.

FIG. 62 is a flowchart providing exemplary additional details of theprocessing of FIG. 61.

FIG. 63 is a flowchart providing exemplary additional details of anotherembodiment of the processing of FIG. 61.

FIG. 64 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for performingon-the-fly head depopulation.

FIG. 65 is a flowchart representing another exemplary method operablewithin a storage device controller (e.g., disk controller) inconjunction with the mapping features and aspects discussed herein abovefor performing on-the-fly head depopulation.

FIG. 66 is a flowchart providing exemplary additional details of theprocessing of FIG. 65.

FIG. 67 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide writing of thermallead-in sequences to allow a write head to stabilize prior to writinguser supplied data to a recordable media.

FIG. 68 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for writingthermal lead-in sequences for allowing the write head to stabilize.

FIGS. 69-71 are flowcharts representing exemplary methods operablewithin a storage device controller (e.g., disk controller) inconjunction with the mapping features and aspects discussed herein aboveto provide re-mapping of physical blocks to eliminate thermal lead-insequences.

FIG. 72 represents an exemplary data block or sector recorded using athermal lead-in sequence write.

FIG. 73 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to handle a grown defectencountered during a read operation.

FIG. 74 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for handlinggrown defects encountered in a dynamically mapped storage device.

FIG. 75 is a flowchart providing exemplary additional details of theprocessing of FIG. 74.

FIG. 76 is a flowchart providing exemplary additional details of anotherembodiment of the processing of FIG. 74.

FIG. 77 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for handlinggrown defects encountered in the dynamically mapped storage device.

DETAILED DESCRIPTION OF THE DRAWINGS

Write fault error recovery features and aspects hereof rely upon thefoundation of a dynamically mapped storage device as claimed in theParent and as discussed herein below. Following the discussion ofexemplary embodiments of the dynamically mapped storage device is adiscussion of write fault error recovery features and aspects hereofthat allow a dynamically mapped storage device to recover from off-trackposition errors encountered while writing data to the recordable media.

Logical to Physical Indirect Mapping

FIG. 1 is a block diagram describing a disk drive 100 embodying featuresand aspects hereof for indirect mapping of logical block addresses tocorresponding physical disk block addresses. Disk drive 100 includesrotating storage media 102 for recording information using optical ormagnetic modulation techniques. Read/write head 122 is positioned over asurface of rotating disk storage media 102 to record (write) informationon the surface of media 102 and to sense (read) previously recordedinformation therefrom. Read/write head 122 is moved radially betweenconcentric tracks arranged on disk storage media 102 by pivoting arm 120and mechanical actuator 104. Positioning of the read/write head 122 overa particular desired concentric track is controlled by disk controller106. Read/write head 122 may also be referred to as a read head or awrite head, as the reading and writing functions are generallyintegrated into a single device or assembly. Disk controller 106communicates with mechanical actuator 104 and read/write head 122 viapath 150. Disk controller 106 may include host interface element 110 forcommunicating with attached host devices, read/write channel element 112for encoding and decoding information written or read by read/write head122, and servo control 144 for accurately controlling rotational speedof disk storage media 102 and the radial track positioning of read/writehead 122. Disk controller 106 may also be referred to as a disk drivecontroller, drive controller or storage drive controller. A plurality ofdisk platters (i.e., multiple storage media 102) and correspondingread/write heads 122 may be incorporated within a single disk drive suchthat vertically aligned concentric tracks may be accessed simultaneouslyby multiple read/write heads. Such a plurality of aligned tracks istypically referred to as a cylinder. Sectors or physical disk blocks arethen recorded about the circumference of each track of a disk mediasurface.

As is generally known in the disk drive arts as presently practiced, aparticular physical disk block or sector has a fixed size and is locatedby its radial track or cylinder position, a head number (where multipleheads and surfaces are incorporated), and a sector or block number onthat track or cylinder. Further, as presently practiced in the art, hostsystems address the physical disk blocks of a disk drive using a logicalblock address ranging between 0 and N where N is the number of availablephysical disk blocks provided within the disk drive. As presently knownin the art, logical blocks, like physical blocks, are fixed size.Typically, the logical block size is an integral multiple of the size ofthe physical disk block. Disk drive controllers as presently practicedin the art therefore perform a simple mathematical mapping ortranslation between a supplied logical block address and a correspondingphysical disk block address. A logical block address is simply convertedmathematically into a corresponding physical track or cylinder, aphysical head and a physical sector or block on that head and cylinder.

As presently practiced in the art, a disk drive controller may performadditional mapping between logical and physical disk block addresses bysupplying a table for bad blocks in which the data is unreadable due tophysical damage or otherwise. The bad block table may translate a givenoriginal address (either logical block address or physical disk blockaddress) into an alternate or spare address for redirecting host accessfrom an original bad block to a replacement, alternate or spare usableblock.

As noted above, such fixed mapping between logical block addresses andcorresponding physical disk block addresses limits the flexibility toprovide a number of useful features. A key to such problems generallyderives from the requisite mathematical relationship between physicaldisk block size and logical disk block size.

In accordance with features and aspects hereof, indirect logical tophysical mapping element 108 in disk controller 106 provides structureand methods for mapping logical block addresses utilized by host devicesinto corresponding physical disk block addresses for blocks stored onthe disk storage media 102. The indirect mapping structures and methodsprovide independence of the logical block size and physical block sizeto thus enable implementation of numerous enhancements and benefits asdiscussed further herein below.

Those of ordinary skill in the art will recognize that FIG. 1 is merelyintended as exemplary of typical components, structures, and functionswithin a disk drive 100 enhanced in accordance with features and aspectshereof. Numerous equivalent structures and functional elements may beprovided as a matter of design choice to achieve the desiredfunctionality of indirect logical to physical disk block addressmapping. Further, those of ordinary skill in the art will recognize awide variety of additional elements useful in design and operation ofany disk drive 100. Still further, any number of disk storage mediasurfaces and corresponding read/write heads may be provided within adisk drive 100 enhanced in accordance with features and aspects hereof.

FIG. 2 is a block diagram suggesting operation of an indirect logical tophysical mapping element 200 (similar to element 108 of FIG. 1). Thelogical block space 202 comprises a plurality of identically sizedlogical blocks enumerated by a logical block address (“LBA”) rangingfrom 0 through N. The logical block size may be defined by a hostoperating system or file system and may represent any convenient sizefor the particular storage application. In other words, larger logicalblock sizes may be preferred for certain applications such as multimediastreaming or video data recording while smaller block sizes may bepreferred for random access general file storage or databaseapplications. LBA space 202 therefore represents an exemplary sequenceof logical block addresses each representing a corresponding logicalblock of equal, predetermined size.

Disk block space 204 represents physical disk blocks stored andretrieved from the disk storage media of the disk drive. Within a diskdrive controller, the physical disk block space 204 may also beaddressed by a sequential index representation of a plurality of blocksindexed by a sequence identifier (e.g., Z0 through Zn where Zn is thetotal number of physical disk blocks available within the storage mediaof the disk drive). The sequential index Z0 through Zn may also betranslated by mathematical and/or other mapping means into correspondingCHS forms of addressing for lower level read and write operations.

In accordance with the indirect logical to physical mapping featureshereof, mapping element 200 is capable of mapping the fixed size logicalblocks from the logical block space 202 into corresponding portions ofthe physical disk block space 204. The physical disk blocks in thephysical space 204 may be of any size independent of the size of thelogical blocks in the logical space 202. The physical disk blocks may beof equal, fixed sizes or may be variable in size but, in any case, thephysical disk block size is independent of the size of the logicalblocks.

In one aspect hereof as shown in FIG. 2, the physical disk blocks Z0through Zn may be variable in size and thereby adapted to optimizeavailable physical space between servo zones disposed on the diskstorage media surface. As is generally known in the art, specialsequences of information referred to as servo information may berecorded at various intervals in the circumferential direction of eachtrack. Often the area between sequential servo zones may be referred toas a servo wedge in view of its wedge shape or pie shape geometrybetween radially disposed servo zones over the entire radial surface ofthe disk platter. Each physical disk block may therefore be configuredas any appropriate size to optimize utilization of this variable sizedspace within each servo wedge. Hence, Z0 may be larger than Zn becauseit may be located within a wider servo wedge area of the disk mediasurface.

Since the physical disk block size is independent of the logical blocksize utilized by attached host devices, features and aspects hereofallow the physical data block size to vary in accordance with thelocation of the block on the physical disk storage media. For example,as shown in FIG. 3, physical disk blocks at an outer diametercircumference outer diameter track of the disk drive may be larger thanthose at an inner diameter track of the disk drive. For example, blocks301 through 308 may be larger than blocks 311 through 318 positioned ata more inward radial position. In like manner, blocks 311 through 318may be larger than physical blocks 321 through 328 at a still furtherinward radial position.

Returning again to FIG. 2, indirect logical to physical mapping element200 may therefore map the predetermined, fixed sized, logical blocksreferenced by a host device into any portion of any of the fixed orvariable sized physical disk blocks. A logical block boundary (start orend) need not coincide with a physical disk block boundary. As discussedfurther herein below, metadata stored within (or otherwise associatedwith) the physical disk blocks may be used to determine the size of eachphysical block and hence the location of the next physical disk block.

For example, as shown in FIG. 2, logical blocks 3, 4 and 5 in LBA space202 are translated by mapping element 202 to a starting portion ofphysical disk block Z3 and the entirety of disk block Z4 in DBA space204. Logical blocks 8 and 9 are similarly mapped to a starting portionof DBA Zn−1 and the entirety of DBA Zn. Further, logical blocks 11, 12and 13 are mapped to the entirety of physical disk block Z0 and abeginning portion of physical disk block Z1.

Those of ordinary skill in the art will readily recognize that anynumber of logical blocks may be provided in a particular application andany number of disk blocks may be defined within a particular disk driveas appropriate for a particular application. Further, as is evident fromFIG. 2, the logical block size and the physical disk block size may beindependent of one another so as to enable numerous additional featuresand aspects hereof discussed further herein below. Still further, theplurality of physical disk blocks may vary in size as desired for aparticular application to further optimize utilization of the areabetween servo zones (i.e., to fully utilize the physical space availablein each servo wedge).

Indirect logical to physical mapping element 200 of FIG. 2 thereforerepresents any processing means and/or structures and methods thatpermit such flexible mapping of logical block addresses to physical diskblock addresses through indirection while permitting independence of thesize of logical blocks and physical disk blocks. Details of exemplarymethods and structures are presented herein below. Those of ordinaryskill in the art will recognize numerous equivalent methods andstructures for providing such flexible mapping in accordance withfeatures and aspects hereof.

FIG. 4 shows one exemplary structure and technique for achieving thedesired indirect mapping between LBA space 202 and DBA space 204. Alogical block address may be used to determine a correspondingintermediate block address in IBA space 400. The IBA space 400 and theLBA space 202 may utilize the same host defined block size i.e., thelogical block size. This first level of indirect mapping from LBA space202 to IBA space 400 permits the LBA space 202 to be initiallydistributed and later redistributed on the disk drive media surface atvirtually any time in a manner transparent to the host device. Allblocks defined in LBA space 202 may be relocated at any time byoperation of methods and structures in accordance with features andaspects hereof—i.e., any block, not merely a small number of “badblocks” recorded in a small table as previously practiced in the art.

A next level of mapping maps between the IBA space 400 and a quantumdata unit space 402 (“QA space”). All physical storage space availablewithin a disk drive may be broken down into a sequence of smallerquantum units of data. The size of a quantum unit of data may be anyconvenient size in accordance with design choices well known to those ofordinary skill in the art but should be substantially smaller than thelogical block size utilized by a host device. For example, the quantumunit data size may be equal to the size of a computer processor “word”used within the disk drive controller i.e., four bytes in a typical 32bit processing environment or eight bytes in a typical 64 bit processingenvironment. Preferably, the quantum unit data size will match aconvenient word size related to processor and/or DMA movement of dataamong various components within the disk controller. Hence, 32 bits or64 bits may be convenient sizes for typical disk controllerapplications.

Although the logical block size and disk block size are independent ofone another, both the disk block size and the logical block size shouldbe integral multiples of the quantum unit data size. In other words,where the quantum unit data size is, for example, a “quadlet” (32 bits),the logical block size and physical disk block size should both beintegral multiples of the fundamental quadlet quantum unit data size(i.e., integral number of quadlet words).

The IBA space 400 corresponds to associated contiguous sequences ofquantum data units. Pointers or other data structure indicia discussedfurther herein below may be used to translate between an indirect blockaddress and a quantum unit of data address. For example, as depicted inFIG. 4, IBA blocks 0 through 2 correspond with the first fifteen quantumunits of data graphically aligned in FIG. 4 immediately below IBA blocks0, 1 and 2. In like manner IBA blocks 8 through 10 correspond to thequantum unit of data contiguous elements graphically aligned immediatelybelow IBA blocks 8, 9 and 10 in FIG. 4. Similarly IBA blocks n−1 and ncorrespond to the quantum data units graphically aligned immediatelybelow IBA blocks n−1 and n. The translation between an IBA space 400block number and corresponding quantum data units may be a simplemathematical determination.

Lastly, the logical to physical mapping features and aspects hereof maytranslate the QA space 402 into corresponding positions within DBA space204. Where, as shown in FIG. 4, the disk block sizes are variable,mapping between the QA space 402 and the DBA space 204 may be bymathematical means in combination with a table identifying the size ofphysical disk blocks in each cylinder, servo wedge or zone. Where theDBA space 204 comprises equal sized physical disk blocks, thetranslation between the QA space 402 and the DBA space 204 may be bysimple mathematical means.

These multiple levels of mapping provide one exemplary embodiment offeatures and aspects hereof Mapping from the LBA space 202 into the IBAspace 400 allows physical blocks to be relocated at the sole discretionof the disk drive controller transparently with respect to any attachedhost system. Next, the mapping between fixed block sizes such as in theLBA space 202 (and the corresponding blocks in the IBA space 400) andDBA space 204 is accomplished by means of the quantum space 402translation. Since both logical block sizes and physical disk blocksizes should be integral multiples of the quantum unit data size,logical blocks may be translated into corresponding disk block addressesindependent of the respective sizes.

FIGS. 10-11 are flowcharts describing methods useful in conjunction withthe exemplary structures discussed above to provide logical to physicalmapping in processing of host I/O requests. FIG. 10 is a flowchartdescribing a high level view of the operation of a disk drive inaccordance with features and aspects hereof to process an I/O requestusing a logical block address provided by an attached host device.Element 1000 is first operable to map the received starting LBA into acorresponding starting physical DBA where the size of the logical blockand physical disk block are substantially independent. Element 1002 isthen operable to complete processing of the received I/O request usingthe disk block address determined by the mapping process of element1000.

FIG. 11 is a flowchart describing I/O processing of FIG. 10 inadditional exemplary detail. Element 1100 is first operable to determinewhether a received I/O request is a read or write request. If thereceived I/O request is a read request, element 1102 is operable toapply the starting LBA received in the request to a mapping tablestructure (e.g., such as shown in FIG. 4) to determine a correspondinglist of associated indirect block addresses. Element 1104 is thenoperable to translate information in the identified associated list ofIBAs into corresponding starting addresses of quantum units of data(e.g., a list of starting and ending addresses in QA space). Element1106 is then operable to determine the starting and ending DBAs for theidentified contiguous quantum units of data. Element 1108 is thenoperable to perform lower level disk operations to read the requestedcontiguous portions of physical disk blocks. Since the desiredcontiguous quantum units of data may not correspond to starting orending boundaries of disk blocks, the retrieved data may includeportions of disk blocks that precede the desired quantum units of dataand/or that follow the desired quantum units of data. Extraneous datamay be removed by operation of element 1108 and the trimmed data(requested data with extraneous start/end data removed) may then bereturned to the requesting host device.

If element 1100 determines that the received request is a write request,element 1120 determines whether the disk drive is presently ready towrite the requested data. As is generally known in the art, data for awrite request may simply be queued for later posting with the requestedwrite data stored in the cache memory or otherwise managed within thedisk drive controller. If the write operation is to be deferred for alater posting, element 1122 is next operable to queue the request forlater posting and thereby complete this disk write request. Suchtechniques are often referred to as write-back caching in that therequest is completed as soon as the disk drive controller has therequest stored in its local cache memory.

If element 1120 determines that the disk drive may presently proceedwith the requested disk write operation, element 1124 is first operableto coalesce this request's write data with the data of other previouslyqueued write requests. Since physical disk blocks may be variable insize, groups of contiguous related data stored in the disk drivecontrollers write cache memory may be coalesced into a single largerdata frame structure as discussed further herein below. The data framemay coalesce contiguous related data and may span portions of one ormore physical disk blocks. Element 1126 is then operable to locate anappropriate unused contiguous portion of the physical disk storage mediaidentified by a starting disk block address. The unused contiguous diskspace is preferably large enough to contain the coalesced data to bewritten.

The data to be written may include portions of contiguous datapreviously written to the disk drive and now coalesced with new data.This new data frame may be written to a new physical location of thedisk drive storage media and therefore any existing mapping structuresfor indirect block addresses associated with the coalesced data to bewritten are freed by operation of element 1128. Element 1130 is thenoperable to insert a new LBA/IBA mapping entry in the master addressingtable corresponding to the new disk block(s) about to be written.Element 1132 is then operable to add any required padding to the dataframe to be written and so that the lower level disk operations maywrite one or more full disk blocks to the disk storage media. Element1132 then completes the write operation by writing the coalesced,padded, physical blocks formatted as a data frame onto the persistentdisk storage media.

Exemplary Mapping Structures and Methods

The logical to physical mapping described above with respect to FIGS. 10and 11 may be performed in accordance with numerous mapping structuresand techniques that permit indirection of the mapping to enablerelocation of physical disk blocks independent of the host suppliedlogical block addresses and that permit independence of the logicalblock size and physical block size.

The logical to physical mapping implementation suggested by theexemplary structures of FIG. 4 may be implemented as table structures ina RAM memory of the disk drive controller such as exemplary masteraddressing table 500 of FIG. 5. Master addressing table 500 may comprisemultiple sections including, for example, indirection sub-table 502,indirection hash table 504, and system variables 506. Each portion orsection of the exemplary master addressing table 500 is discussedfurther herein below. In general, indirection sub-table 502 comprises anordered list of pointers for translating a contiguous sequence oflogical block addresses (LBAs) into a corresponding sequence of indirectblock addresses (IBAs). Given the potentially large size of such astructure, indirection hash table for 504 provides a rapid index tosections of the larger interaction sub-table 502. Those of ordinaryskill in the art will recognize a variety of similar structures tosegment such a large table such as indirection sub-table 502 for morerapid searching. System variables 506 include numerous metadata valuesand other control variables useful in managing master addressing table500. For example, system variables 506 may include a sequence numberused to identify a chronological order for various copies of the masteraddressing table as well as the order of data frames added to the diskstorage relative to a copy of the master addressing table 500. Thesequence numbers in the master addressing table(s) and the data framesmay be used to synchronize various pointer entries with a correspondingversion of the master addressing table.

The master addressing table is preferably maintained within RAM memoryof the disk controller. Since the disk controller's RAM memory istypically a volatile memory, the master addressing table 500 isperiodically written to reserved areas of the disk storage media. Suchreserved areas are preferably excluded from the DBA space discussedabove used for storage of host device supplied data. Storing the masteraddressing table 500 in such reserved locations of the disk drivestorage media assures that the logical and physical address spaces andmappings there between may be recovered in case of power failure duringoperation of the disk drive. Further, multiple copies of the masteraddressing table may be stored in different locations of the disk driveto further enhance reliability of the retention of the address mappingstructures. Still further, each of such multiple copies may represent adifferent snapshot in time of the present mapping data stored on thedisk drive storage media. Such periodic snapshots of the masteraddressing table maintained on the disk storage media permit rollback ofthe mapping structures to earlier points in time. Such a rollbackfeature permits managed reliability for the contents of the disk drive.

The structure of entries in the various portions of the masteraddressing table 500 is exemplified in FIG. 6 and exemplary use of suchstructures is depicted in FIG. 7. Referring first to FIG. 7, theindirection hash table 504 comprises a plurality of hash table entrieseach pointing to the starting location of a segment of the indirectionsub-table. Each segment or region of the sub-table 502 comprises aplurality of indirection sub-table entries each mapping a starting LBAto a corresponding IBA. The indirection hash table 504 therefore permitsmore rapid access to segments or portions of the potentially largeindirection sub-table 502. As shown in FIG. 7, an upper portion 706 ofan exemplary 32 bit LBA 704 may be used as an index into indirectionhash table 504. The entry so located may then be used as a start pointerfor the corresponding segment of the indirection sub-table 502. A lowerportion 708 of bits in the exemplary LBA 704 may then be used to searchthe identified segment or region of the interaction sub-table 502.

FIG. 6 shows an exemplary format for each entry 600 of the hash table504 and each entry 610 of the sub-table 502. The hash table entry 600includes a start pointer 602 to the start of the sub-table 502 sectioncorresponding to the hash entry's index value (i.e., the upper bitportion of an applied LBA). A sub-table page/segment size 604 indicatesthe number of entries in the segment to which the start pointer 602points. Each sub-table entry 610 includes a start LBA 612 and an end LBA614 defining the range of LBAs mapped by this entry to correspondingIBAs. The start IBA 616 indicates the first IBA of the contiguous IBAsto which the corresponding range of LBAs is mapped.

Those of ordinary skill in the art will recognize numerous equivalentstructures for providing the desired indirect mapping features. Thestructures of FIGS. 5-7 are therefore merely intended as exemplary ofone possible set of data structures for providing the desired indirectmapping and independence of logical and physical disk block sizes.

FIG. 12 is a flowchart describing additional details of an exemplarylogical to physical mapping step utilizing the exemplary data structuresdescribed herein with respect to FIGS. 5-7. Element 1200 is firstoperable to apply a first portion (e.g., 706 of FIG. 7) of the receivedLBA to a hash table (e.g., 504 of FIGS. 5 and 7) to locate a segment orportion of the indirection sub-table (e.g., 502 of FIGS. 5 and 7). Asabove, the indirection sub-table entries provide mapping of a startingLBA to a corresponding starting IBA for a sequence of contiguous blocks.The hash table entry therefore points to a segment or portion of theindirection sub-table representing a contiguous segment of logicalblocks. As noted above in FIG. 6, the entry may also include a size ofthe segment to be searched. Element 1202 then searches the identifiedsegment to find the specific starting IBA corresponding to the secondportion of the supplied LBA. Those of ordinary skill in the art willrecognize that the number of bits used for the first portion as an indexinto the hash table and used for the second portion as a search term forsearching the sub-table is a matter of design choice in trading off hashtable size versus sequential searching of an identified segment.Further, those of ordinary skill in the art will recognize well-knownsearch techniques such as binary search techniques for searching theordered list represented by the identified segment of the sub-table.

Elements 1204 and 1208 are then operable to determine the particularquantum units of data corresponding to be identified starting IBA.Specifically, element 1204 determines the quantum address (QA)corresponding to the starting IBA and element 1208 maps the QA into acorresponding starting and ending DBA using mathematical translationtechniques optionally in conjunction with a table look up associatedwith variable length physical block sizes. Such mathematicaltranslations and table lookup processing techniques are well known tothose of ordinary skill in the art.

Mapping Table Copies, Regeneration and Data Frames

The indirection sub-table 502 (of FIGS. 5 and 7) may grow and shrink asportions of the disk drive storage media are utilized. The structure maybe maintained as any of several well known data structures to simplifysuch expansion and contraction. A simple vector of entries may be usedand entries shifted up or down as entries are deleted or added. Eachsegment of portion may be so managed as a separate vector or the varioussegments may be managed together such that the entire sub-table is asingle vector of memory. Numerous well known dynamic memory managementstructures and techniques may be utilized to aid in managing the size ofa working copy of the master addressing table stored in RAM memory ofthe disk drive controller. In particular, in one exemplary embodiment,the master addressing table and cache memory space may be commingled andmanaged such that the master addressing table may grow and shrink byallocating and freeing memory in cooperation with corresponding sizemanagement of cache memory. In other words, a single pool of physicalmemory may be used for both allocation in the master addressing tableand for data caching features within the disk drive controller. Again,those of ordinary skill in the art will recognize numerous equivalentstructures and techniques for dynamically managing memory used eitherfor caching or for addressing tables associated with features andaspects hereof.

Since the RAM memory working copy of the master addressing table istypically stored in a volatile memory within the disk drive controller,it is preferable to periodically update a copy of the master table savedon the disk drive storage media for persistent storage. In view of thelarge size and the latencies associated with disk media access, themaster addressing table should not be updated on disk each time a changeis made. Rather, the table may be copied to a reserved area of the diskperiodically in response to changes made thereto. When the disk drive ispowered up, the master addressing table last stored on the disk mediamay be used to initialize the RAM copy of the master addressing table.However, the master addressing table most recently stored on disk willlikely be inconsistent with the actual data stored on disk i.e., willnot accurately reflect data written to the disk blocks but for which thedisk copy of the master tables did not get recorded prior to disk powerdown.

To address this condition, host supplied data is written to the diskwith structured metadata that permits the RAM copy of the mapping tablesto be updated to reflect data actually recorded on the disk storagemedia. As discussed further herein below, data is recorded in the formof a data frame where metadata in each data frame maintains a linkedlist of all data frames linked in the chronological order in which theywere written to the disk. The data frame metadata may be used toreconstruct the master addressing table by sequentially traversing alinked list of data stored on the disk drive physical storage media.Since such traversal of data stored on the disk drive storage media canalso be very time consuming at power up of the disk drive, a relativelyrecent version of the addressing tables is located on the disk drivemedia and used as a starting point for the traversal of data frames. Toreduce the time for traversing the data frames at power upinitialization of the disk drive, it is preferable that the addressingtables be frequently written to the disk media so that the addressingtables are a more accurate representation of the data frames presentlystored on the disk. Conversely, in view of the potentially large size ofthe master addressing tables, recording the table on the persistent diskdrive storage media can be time consuming. Numerous techniques andstructures will be readily apparent to those of ordinary skill in theart to establish an appropriate performance tradeoff between runtimeperformance during normal operation of the disk drive and power upprocessing time required to prepare the disk drive for normal operation.For example, the master addressing tables may be updated on the diskdrive storage media nearly constantly during idle periods in the diskdrive if (i.e., when no host device request is presently pending) andmay be less frequently updated during processing of host based requests.

When the disk drive is initially powered up, the working copy of themaster addressing table must be retrieved into memory RAM memory of thedisk drive controller and then may need to be updated to reflect anydata frames written to physical disk blocks since the last posted updateof the master addressing table to the persistent disk media storage. Themetadata of the master addressing table (i.e., system variable thereof)and the metadata of the data frames may be used to reduce the timerequired to initialize the disk drive for normal operation.

First, where multiple copies of the master addressing table are recordedat various locations of the disk drive storage media, the copy with themost recent (e.g., highest) sequence number will be retrieved asrepresenting the most recently saved version of the master addressingtable. The metadata of the master addressing table preferably includes apointer to the last data frame to be written to the disk prior towriting the corresponding copy of the master tables to the disk media.This last data frame may be used as a starting point to reduce thenumber of data frames that must be traversed to update the RAM copy ofthe initialized master addressing tables.

FIG. 19 is a flowchart describing a method associated with features andaspects hereof for retrieving and updating master addressing tables fromthe disk drive storage media to perform power on of the initializationof a disk drive. Element 1900 is first operable to locate and retrievethe most recent saved copy of the master addressing table. As notedabove, numerous chronological snapshots of the master addressing tablemay be stored on the disk drive persistent storage media. A sequencenumber entry in the system variables field of each saved copy may beused to identify the most recent of the multiple copies (e.g., thathaving the highest sequence number). Having so retrieved the most recentcopy into RAM memory of the disk drive controller, element 1902 is thenoperable to locate the last data frame written to disk prior to writingof the most recent master addressing table. The last data frame may bedetermined according to the system variables in the retrieved masteraddressing table. As noted above and discussed further herein below,each data frame includes metadata including a sequence number indicatingits chronological order of writing with respect to the sequence numberof a corresponding master addressing table and with respect to otherdata frames. Data frames following the last identified data frame in thejust read master addressing table are then traversed to update the justread master addressing table. Element 1904 represents processing totraverse the linked list of newer data frames starting at the identifiedlast data frame in the retrieved master addressing table. For each dataframe traversed, the master addressing table read into RAM is updatedaccordingly until no further data frames are encountered in thetraversal. Hence, the master addressing table in RAM memory of the diskdrive controller is updated during power up. Normal processing commenceswith periodic saving of updates the master addressing table as notedabove.

As noted above, to aid in managing mapping features and aspects hereof,a data frame structure may be utilized that includes management metadatato permit coalescing of contiguous blocks provided by the host requestand to enable the mapping features and aspects hereof. In coalescing,when a plurality of contiguous quantum units of data are to be writtento the disk drive, all available contiguous quantum units with data areaggregated together to create a single data frame to be written to oneor more physical disk blocks of the disk drive storage media. Thestructure of the data frame enables this coalescing feature.

FIG. 8 is a block diagram describing one exemplary embodiment of a dataframe useful for managing mapping and other features and aspects hereof.The data frame preferably may include a leading metadata 802 used todefine the format and layout of portions of the data frame to follow.The leading metadata 802 is preferably a fixed size field that includesinformation such as the sequence number and size of the variable deltatable and data portion that follows the leading metadata 802. The deltatable 804 may follow the leading metadata field 802 and is a variablelength table of entries providing a list of logical block addressesrepresented by the data frame. Each delta table 804 entry may include alogical block address 810 and the size 812 of the contiguous logicalblocks that make up the data portion 806 that may follow. The deltatable 804 entries are preferably maintained in sorted order according tostarting logical block address. The delta table 804 therefore provides amap of the contiguous data portion 806 that immediately follows thedelta table 804. The lead out field 808 is used as a delimiter for theframe and points to the physical location of the next data frame on thedisk drive persistent storage media next in accordance with thechronological order in which the data frames are written. The lead outfield 808 may also be constant in size and, through its linked listfield, permits traversal of all data frames in the chronological orderin which they were written.

Physical Space Defragmentation

Using the linked list structure of all data frames, the physical spaceof the disk drive storage media may be periodically compacted. FIG. 9 isa block diagram describing a method for compacting the physical space onthe disk drive storage media. Each rectangular shaded portion of FIG. 9represents a data frame as described above.

It is preferable to maintain a minimum write band 900 of available spaceon the disk drive storage media so as to avoid the possibility of anoverrun condition during disk write operations. The size of the writeband 900 is a matter of design choice and may be a function of, forexample, the write cache size of the disk drive controller. In order tomaintain an appropriate write band, it may be necessary to periodicallyrelocate blocks ahead of the write band—e.g., it may be necessary todefragment the physical space on the disk drive by moving blocks aheadof the write band to available space preceding or behind the write band.Such circular decompression is suggested by the movement of blocks shownin FIG. 9.

Numerous techniques and structures for such circular compression(compaction) of the physical disk space will be readily apparent tothose of ordinary skilled in the art. The indirect mapping and variablesize data block features and aspects hereof enable such defragmentationand compaction while the indirect mapping allows relocation of physicalstorage space to be performed transparently with respect to host systemsand devices.

FIG. 13 is a flowchart describing high level processing techniquesassociated with defragmentation of the physical storage space. Element1300 is first operable to locate data frames ahead of the current writeband position. Data frames may be deemed “ahead” of the current writeband position if they are located in physical DBAs sequentially higherthan the DBAs corresponding to the current write band position. Element1302 then attempts to coalesce multiple located data frames into a newdata frame to be written in contiguous, available physical disk blocks.Element 1304 then represents processing to write the new, coalesced dataframe at physical disk block addresses representing unused physicalspace preceding the current write band position. If the writing of thecoalesced new data frame is successful, element 1306 is operable toupdate the IBA pointers associated with the newly relocated data frameto reflect the new physical position of the associated indirect blocks.Element 1306 is also operable to mark the previous data frames, nowcoalesced into a new data frame, as free and available for re-use. Inparticular, the old data frames may be unlinked from the linked listqueue of data frames written to the disk. Element 1308 then determineswhether additional free space ahead of the current write band positionis still required. If so, processing continues looping back to element1300 to look for additional data frames ahead of the current write bandposition that may be relocated. If no additional space is needed at thistime, element 1310 is operable to await the next periodic time foroperation of the method. The method of FIG. 13 may run continuously as abackground process in the disk drive controller and therefore may bescheduled at optimal times or may simply run continuously as a lowpriority background task. Eventually, when appropriate to continueoperation, processing of the method continues looping back to element1300 to attempt to locate additional data frames to be relocatedrelative to the current write band position.

Mapping Structure Defragmentation

As data is written and re-written and as data frames are relocated, themapping table structures may also become fragmented. In particular, theexemplary indirection sub-table discussed above with respect to FIGS.5-7 may require defragmentation and compaction. Simple block memorymoves may achieve the desired compaction where simple vectors ofpointers are used as described above in the exemplary embodiment ofFIGS. 5-7. Where more complex linked list queues or other more complexdata structures are employed, other defragmentation and compactiontechniques and structures may be employed as a matter of design choicereadily recognized by those of ordinary skill in the art.

Where, for example, a logically contiguous file of information iswritten spanning a significant period of time, the logically contiguousblocks may be physically dispersed over the physical disk block space.Further, the indirect mapping tables will have a corresponding pluralityof indirection mapping entries in the table structures described above.Periodically, these mapping tables may be scanned to locate suchfragmented physical blocks that correspond to contiguous logical blocks.This defragmentation procedure may then gather the dispersed blocks,read them and re-write them in a new, contiguous physical data frame soas to generate a single indirect mapping table entry. The previousplurality of mapping table entries and corresponding fragments ofphysical disk blocks may then be recouped for re-use and the mappingtable structures may be correspondingly compressed.

Methods and structures useful for such defragmentation will be readilyapparent to those skilled in the art in view of the above mapping tablesformats and data frame formats discussed above.

Disk Drive Data Compression

Features and aspects hereof associated with indirect mapping andindependence of the logical and physical block sizes also permitcompression features to be employed within the disk drive of controller.Whereas prior techniques generally performed compression at the hostdriver level or operating system level, indirect mapping and independentblock size features hereof permit data compression to be performedwithin the disk drive transparently to host systems, drivers, andapplications.

FIG. 14 is a block diagram of a disk controller 1400 in which mappingfeatures and aspects discussed above may be embodied. Disk controller1400 may include control logic and host interface 1402 for hostinteraction and for overall control of the disk drive. Data buffer 1404is a memory used typically as a cache or staging buffer for exchanges ofinformation between the disk storage media through read/write channel1410. Compression engines 1406 represent one or more compressionassistance circuits for performing on-the-fly data compression as datais moved into or out of data buffer 1404. Error control element 1408 isa circuit utilized by disk controller 1400 to perform error codegeneration and checking in association with data transfers throughread/write channel 1410 to or from the storage media. All the componentsof disk controller 1400 may communicate via communication path 1412. Inpractice, those of ordinary skill in the art will recognize a variety ofoptimal communication paths and buses for dedicating particularinformation exchanges to particular segmented, dedicated buses andcommunication paths.

As noted above, logical to physical mapping features and aspects hereofalong with independent logical and physical disk block size features andaspects hereof enable on-the-fly compression to be utilized within thedisk controller 1400. As a matter of design choice, compression engines1406 may compress data as it is exchanged between the data buffer 1404and the host interface 1402 moving data between the host system and thedisk controller 1400. In such a configuration, compression engines 1406compress received data from the host system prior to storing the data inthe data buffer 1404 and decompress data from data buffer 1404 prior toreturning the data to a host system. In an alternate embodiment,compression engines 1406 may compress data as it is exchanged betweendata buffer 1404 and read/write channel 1410. Data to be written to thedisk storage media through read/write channel 1410 may be compressed asit is retrieved from data buffer 1404 for transmission to read/writechannel 1410. Conversely, data read from the storage media throughread/write channel 1410 may be decompressed by decompression engines1406 prior to storing the read data into data buffer 1404.

Depending on the particular data compression techniques utilized and theconfiguration for compressing data within disk controller 1400, one ormore compression engines 1406 may be operable in parallel to improveperformance of compression techniques within the disk controller 1400.

Those of ordinary skill in the art will recognize that the block diagramof FIG. 14 is intended merely as representative of one possibleconfiguration of features within an improved disk controller providingon-the-fly compression and decompression. Numerous equivalent structuresand additional features will be readily apparent to those of ordinaryskill and the art to permit on-the-fly compression and decompression ofdata within the disk controller in accordance with interactive mappingfeatures and aspects hereof and in accordance with independent logicaland physical disk block size features and aspects hereof.

A variety of benefits may be derived from compression of data within adisk drive controller. One clear benefit derives from simply increasingthe capacity of the disk drive storage media. Although some overheadmetadata is required to manage the compressed data, a common compressionratio of 2:1 of the host supplied data (i.e., for typical text files)may achieve a significant benefit in improved capacity of the storagedevice disk drive. A second benefit associated with on-the-flycompression within a disk drive controller derives from the improvederror correction capabilities to thereby enhance data reliability in adisk drive. First, by merely compressing the data before recording thedata on the disk drive storage media, existing error control codes(“ECC”) provide error correction for the compressed data. Since thecompressed data represents more user data in decompressed form, the sameerror correction capabilities normally existing in the disk driveprovide improved bit error rates when measured against the volume ofdecompressed user data represented by the compressed data on disk.Secondly, by compressing the data portion stored on the disk drivestorage media, the recouped space may be used for generation and storageof additional error correction bits to still further improve the biterror rate for data stored on the disk storage media.

FIGS. 15 and 16 graphically demonstrate the improved error correctionfeatures attainable by compressing data within the disk drivecontroller. FIG. 15 represents a typical data block or sector aspresently recorded in typical disk drive storage media. A preamblesequence 1500 provides a header portion for information regarding theparticular disk block such as block number and other metadatainformation. The sync field 1502 provides a standard bit pattern toallow the read/write channel phase lock loop controls to synchronize onthe upcoming uncompressed data field 1504. As above, the data field maybe one or more data frames with associated metadata linking the framewith other frames in chronological order. Following the uncompresseddata field 1504 is an error correction code field 1506 to provide errorcorrecting bits for detecting and correcting various bit errorsencountered in reading the uncompressed data 1504 from the disk storagemedia. FIG. 16 represents a similar disk block or sector with compresseddata in compressed data field 1602. An additional header fieldrepresenting compression attributes 1600 may be added to the disk blockto represent parameters of the compression algorithm applied to compressthe data. In addition, as noted above, some of the recovered space dueto the compression of data may optionally be used for additional errorcorrection bits in the ECC+ field 1604.

FIGS. 17 and 18 graphically represent the benefit of improved storagecapacity derived from compression of host supplied data by the diskcontroller. FIG. 17 depicts consecutive, contiguous physical disk blocksstored on a typical disk drive in accordance with presently knownrecording techniques. As above in FIG. 15, each disk block may include apreamble 1700, a sync field 1702, uncompressed data field 1704, and acorresponding error correction code field 1706. In like manner, a nextcontiguous disk block may include its own preamble 1710, sync field1712, uncompressed data 1714, and error correcting code 1716.

In accordance with features and aspects hereof, a disk block may vary insize such that formerly contiguous independent disk blocks may becompressed into a smaller compressed data field 1802 as shown in FIG.18. A preamble field 1700 and a sync field 1702 may function asdescribed above in FIG. 17. A compression attribute field 1800 maydescribe parameters and attributes of the compression used forcompressing the user data into compressed data field 1802. ECC field1804 then provides error correction bits for the compressed, combineddata from the formerly uncompressed data are represented by uncompresseddata field 1704 and uncompressed data field 1714 described above withrespect to FIG. 17. Thus, a compressed frame as shown in FIG. 18 maydramatically improve the physical capacity of a disk drive despite theaddition of a compression header field 1800 to the standard disk frameformat.

Unwind

Other features and aspects hereof represent other benefits derived fromthe flexible mapping features and aspects hereof and the independence ofthe logical and physical block sizes.

As noted above, the master addressing table structures (or similarmapping structures) may be saved in multiple reserved locations of thedisk drive. Where the multiple copies are maintained as chronologicalsnapshots of the mapping structures, the contents of the disk drive maybe restored or “unwound” to an earlier state reflected by the saved,earlier master addressing tables. Traversing forward through the linkedlist of data frames since the data frame last written as saved in arestored master addressing table, the “unwinding” may be processedthrough to any specific write operation.

Duplicating the master addressing table as stored on the disk drivestorage media provides the unwinding feature as above as well asgenerally enhancing the reliability of the disk drive. Failure to readone copy of the master addressing table does not necessarily prevent useof the disk drive. Other (perhaps earlier) copies of the masteraddressing tables may be usable to initialize the disk drive.

Increased Track Density

Another benefit enabled by mapping features and aspects hereof providesincreased radial track density in storing data on the disk drive storagemedia surface. When writing data on a magnetic disk drive storage media,the magnitude, shape, and direction of the magnetic field applied to thedisk surface are critical factors in the quality of the recorded signalto be read. It is a well known problem in the disk drive arts that alarger magnetic field may improve the recorded signal quality but alsoreduces storage capacity in that larger gaps may be required betweeneach track. The gap between tracks is needed to prevent writing of onetrack from unintentionally erasing (overwriting) data on an adjacenttrack. Though there are slight differences in the nature of the problem,this issue arises in both longitudinal recording and vertical(perpendicular) recording techniques well known in the arts.

Mapping features and aspects hereof permit logical blocks to be writtenin any desired physical order on the disk drive surface. In particular,features and aspects hereof suggest that data may be recorded onphysical disk blocks generally in a sequential order (i.e., from innerdiameter tracks/cylinders to outer diameter or vice versa). By generallyadvancing the read/write head in one direction (i.e., from innerdiameter to outer diameter or vice versa), data that sequentiallypreceded this write may be saved while data on tracks/cylinders thatwill sequentially follow the current writing operation may beoverwritten with impunity.

FIG. 20 is a block diagram that schematically represents consecutivewritten tracks using such a read/write head configuration that, inconjunction with mapping features and aspects hereof, permits improvedtrack density. Tracks 2010, 2012, and 2014 have a nominal track pitch2002 that is less than the write head width 2000. Each track 2010, 2012,and 2014 has a track centerline indicated by a corresponding thickerdashed line. In accordance with mapping features and aspects hereof,tracks 2010, 2012, and 2014 are written in sequential order from theinner diameter of the disk surface (ID) to the out diameter (OD). Priortechniques devoid of the mapping features and aspects hereof could notassure such sequential writing of tracks except in particular,application specific circumstances (such as data logging or video datacapture where an entire disk drive capacity may be filled by the captureof sequential data). By contrast, mapping features and aspects hereofassure the ability to sequentially order track writes as indicated inFIG. 20.

Assuring such a sequential order of adjacent track writes allows thetracks to be more closely spaced because unwritten tracks ahead of thecurrent track position will not contain data that must be retained.Thus, mapping features and aspects hereof obviate the need for gapsbetween adjacent tracks and thereby allow a higher tack density to berecorded on the disk drive. For example, track 2010 may be writtenfirst. Later, as more logical block writes are requested by hostdevices, track 2012 may be written the next/adjacent track in thedirection from ID to OD. Track 2012 is written such that its inner-mostedge overlaps the outermost portion of the earlier written track 2010.However, the overlap is designed such that the data of earlier track2010 is still accurately readable. Similarly, next sequential track 2014overlaps the outer portions of earlier track 2012, and so on.

Though features and aspects hereof permit such generally sequentialwriting of tracks, it may be necessary at times to re-write earlierrecorded tracks. For example, mechanical shock or vibration may cause atemporary “off track” condition where the read/write head is temporarilymoved off the intended track position. In such an off-track condition,continued writing may overwrite previously written data fromsequentially earlier track writes. Well known servo and other controllogic in disk drives reduces the amount of such overwritten data butnone-the-less, some overwritten data may need to be recovered. Priortechniques generally provided wide enough inter-track gaps to avoid theneed for such data recovery. However, with the narrower gaps (i.e., nogaps) between tracks, some mechanism must be provided to permit possiblere-writing of earlier sequential written tracks.

Mapping features and aspects hereof also provide that the most recentlywritten blocks written in preceding, sequentially earlier tracks willremain in the disk controller's cache memory. Earlier tracks that mayrequire re-writing may therefore be re-written from the data remainingin cache memory. However, the size of cache memory is not limitless.Further, wherever a first track is to be re-written, care must be takento not overwrite still earlier data in still earlier adjacent tracks(track data that may no longer reside in cache memory).

In accordance with features and aspects hereof, the tightly packedtracks of each disk surface may have period guard bands intermingledi.e., periodic inter-track gaps between groupings of tracks. FIG. 21 isa schematic diagram showing a disk surface 2100 with a plurality oftracks 2102 for recording of data. Periodically interspersed betweengroupings of tracks are inter-track gaps 2104 (guard bands) to providespacing between adjacent groups of tracks. The number of tracks in eachsuch group may be determined as a matter of design choice based, inpart, on the size of the write cache memory in the disk controller.

Dynamic Multiple Indirections

It remains an ongoing problem in all storage devices to improvereliability and performance of the storage device. A particular problemwith reliability of storage devices occurs when problems appear in asubsection of the storage device affecting the reliability of the datastored in the subsection. Since data is typically stored in only asingle subsection of the storage device, if the subsection incursproblems, then the data may be permanently lost.

Since all user data written to the dynamically mapped storage device isdynamically mapped from the user supplied logical address space (logicalblock addresses or LBAs) to the physical disk block address space (diskblock addresses or DBAs—blocks of variable size relative to the LBAsize), features and aspects hereof permit generation of multipleindirection table entries for any user data written to the storagedevice recordable media. In general the indirection table entries mayinclude multiple entries for a given LBA—each corresponding to adifferent copy of the data mapped from the same LBA space address to adifferent physical address. Providing multiple copies (multipleindirections) for user supplied data in the storage device improvesreliability of the storage device by reducing the probability of loss ofuser data for various failure modes of the storage device. For example,if a particular physical area of the recordable media begins to exhibiterrors (hard errors or soft recoverable errors), another copy of thesame user data (another of the multiple indirections stored on thestorage device) may be accessed to permit recovery thereof and to permitcontinued operation of the storage device.

For example, each logical block could be duplicated in two (or more)corresponding physical disk blocks of the disk drive. Each copy has amapping table entry mapping the same LBA for the logical block todifferent physical address space locations. A first copy of the data fora logical block could be on a first disk media surface (using acorresponding first read/write channel/head) and a second copy may bestored on a separate surface (using its corresponding read/writechannel/head). Or, for example, a first copy of a logical block may bestored on an inner radial half of the selected surface of the disk driveand a second copy of the same logical block may be stored on an outerradial half of the same surface of the disk drive.

In addition to enhancing reliability, duplicate copies of the hostsupplied stored data may enhance performance of the dynamically mappedstorage device. Where multiple copies of host supplied data are stored,the copy which is most quickly accessible given the current operatingstate of the storage device may be accessed to reduce latency delays andhence improve throughput of the storage device. For example, if a firstcopy of the data is stored at a rotational position of a particulartrack (on rotating recordable media in the storage device), and a secondduplicated copy happens to be stored at a different rotational positionof the same track, which ever copy will next be encountered by theread/write head as the media continues to rotate may be accessed. Thusrotational latencies may be reduced. Or, for example, where multiplecopies of data are stored at different radial track positions, whicheverof the multiple tracks may be most rapidly accessed may be used toreturn requested data to a host system.

Still further, in addition to simple duplication of data blocks, otherforms of redundancy information may be generated by the disk drive andstored on the disk drive in a manner transparent to the attached hostsystem(s). Such redundancy may entail any form of enhanced errordetection and correction including, for example, RAID-like XOR parity orother redundancy information. All such redundancy information may begenerated, stored and checked by local processing features of the diskdrive controller. By virtue of the mapping features and aspects hereof,this additional redundancy information may be hidden from the attachedhost systems.

When user data is received, the currently used physical capacity of thestorage device may be inspected to determine if there is sufficientspace to replicate the user supplied data when written. If so,performance information regarding operation of the storage device may bereviewed by the storage device controller to determine the number ofredundant copies that may be beneficial and to determine preferredphysical areas in which the replicated data may be recorded (e.g.,different surface/head, different radial position, different rotationalposition, or combinations of the three).

So long as the ratio of stored logical content to total physicalcapacity remains lower than about 0.5, all logical blocks of user datamay be mapped to at least two different physical locations. As the ratiomoves toward 0.5 and higher, features and aspects hereof may selectivelydetermine which user data blocks need be duplicated. For example,features and aspects hereof may select blocks deemed to be critical suchas file directory and FAT table structures stored as user data on thestorage device. Or, for example, data that is observed to be frequentlyaccessed may be selected for duplication as critical data based on itsfrequency of access. Other less critical data may be mapped to only asingle physical location (i.e., not replicated). Numerous otherheuristic rules will be readily apparent to those of ordinary skill inthe art to identify critical data that may be selected by the storagedevice for replication in accordance with features and aspects hereof.In like manner, as the ratio of logical content to physical capacitymoves higher, duplicate copies of less critical user data previouslyreplicated on the storage device may be eliminated.

To add duplicate copies requires merely updating the mapping tables usedto map user supplied logical block addresses to physical disk blockaddresses (plus the access time to actually write the additional,duplicated data). To remove a duplicate copy, the mapping tables may besimply updated to remove the mapping table entry between the LBA spaceand the corresponding additional physical space of the duplicate copy tobe removed. The physical space so recovered from the duplicated copiesmay then be used for replicating other host supplied data, or, if needbe, to recover space to permit further writing of host data withoutduplication.

Various performance metrics of the operation of the storage device maybe used to determine the need for such duplication of user data. Forexample, read/write head operating temperature, bit error rates fromreading of data, shock and vibration event statistics, etc. may all beused to aid in determining the current level of reliability of theoperating storage device and hence the need for more or less user dataduplication. For example, if a particular read/write head of the storagedevice begins exhibiting higher error rates suggesting a possiblefailure of that head assembly, user data that may be currently mapped tothe physical space of the affected area may also be replicated toanother physical area by addition of an appropriate mapping table entryand duplication of the data to the other physical area.

Logical data blocks replicated in multiple physical locations may bereplicated at different radial positions on the storage device and/or atdifferent rotational offsets at the same radial position of the diskdrive. For example, by locating a duplicate mapped version of a hostsupplied logical block at the same radial position but rotationallydisplaced from the first copy of the block, rotational latencies may bereduced when accessing that mapped logical block. When access to data isrequested and multiple copies are logically mapped to the disk, the diskdrive may elect to use whichever copy of the replicated user data isrotationally closer to the current rotational position of the read/writehead relative to the rotating media to thus reduce rotational latency incompleting the request. In like manner, duplicated copies of mapped userdata may be placed at a different radial position. Where data accesspatterns (as analyzed by the disk drive controller) tend to be highlyrandomized, the nearest radial position of such multiple copies of therequested data may be accessed. Thus, seek latencies may be reduced in arandomized data access application. Still further, multiple copies ofuser data may be distributed over multiple heads or surfaces of the diskdrive with or without rotational displacements. Thus a copy of therequested data may reside on a presently utilized head to reduce theneed for head switch delays. Still further, those of ordinary skill inthe art will readily recognize that the above strategies fordistributing copies of duplicated host supplied data may be combined.For example, copies of host supplied data may be distributed atdifferent rotational positions on the same track (i.e., same radialposition of the same head) and other copies may be distributed atdifferent radial positions and/or on different read/write heads.

FIG. 22 is a schematic representation of a single surface of a rotatingdisk recordable media. The recordable media surface 2200 comprises aplurality of concentric tracks logically laid out from an inner diameterthrough an outer diameter. In accordance with the multiple indirectionfeatures and aspects hereof, multiple copies of host supplied data maybe recorded in various physical locations of surface 2200. As notedabove, such multiple copies may be distributed in differing physicallocations so as to improve performance and/or reliability of thedynamically mapped storage device. For example, a first copy 2202 andsecond copy 2208 of host supplied data may be mapped to differentrotational positions within the same radial track position. Furthercopies of the host supplied data 2204 and 2206 may be located at anotherradial track position. Such diverse locations may improve performance ofthe dynamically mapped storage device in that whichever of the multiplecopies (2202 through 2208) is nearest the present location of theread/write head (not shown) may be utilized to access requested data.For example, if the read/write head is presently positioned on the trackcontaining copies 2202 and 2208, whichever copy will be next encounteredby the read/write head as recordable media surface 2200 continues torotate may be utilized to access the requested data. Alternatively,where the dynamically mapped storage device is utilized for highlyrandomized access, whichever radial track position containing a copy ofthe requested data is closer to the current read/write head position maybe utilized to access requested data. Thus, the radial track positioncontaining copies 2202 and 2208 may be utilized or the radial trackposition containing copies 2204 and 2206 may be utilized—whichever trackposition is closer to the current position of the read/write head. Thusseek time and associated head settling time may be reduced if the radialtrack position is closer to the current track position of the read/writehead.

In addition, such multiple copies may be located on the rotatingrecordable media 2200 so as to improve reliability by reducing theprobability of encountering an error in accessing requested data. Forexample, where current operating parameters of the dynamically mappedstorage device indicate a possible failure arising near the radial trackposition containing copies 2202 and 2208, the alternate copies on theradial track position containing copies 2204 and 2206 may be accessed toreduce the probability of an error when reading the requested data. Overtime, as a possible error condition in fact arises on the inner radialtrack position, copies 2202 and 2208 may be relocated to other physicallocations to continue operation of the dynamically mapped storage devicewith enhanced reliability and/or performance.

As shown in FIG. 22, where copies are positioned at different rotationalpositions of the same radial track position, it may be advantageous toposition each of two copies at 180° offsets in the direction ofrotation—e.g., equidistant around the circumference of the radial trackposition. Similarly, where more than two copies of host supplied dataare recorded on the same radial track position they may be similarlypositioned equidistant from one another around the circumference of theselected radial track position. Thus, performance of the dynamicallymapped storage device is enhanced by assuring some copy of the hostsupplied data will be close to the current rotational position of theread/write head over the rotating recordable media surface 2200. Also asshown in FIG. 22, where multiple copies of host supplied data arephysically located at different radial track positions, a first copy maybe located on inner radial track positions while a second copy may belocated at outer radial track positions. Thus, multiple copies arephysically separated to avoid potential errors arising from damage tothe recordable media rotating surface 2200 at a particular radialposition.

Not shown in FIG. 22 but readily apparent to those of ordinary skilledin the art is a structure wherein multiple copies may be physicallypositioned on different surfaces of a multi-surface dynamically mappedstorage device. Thus, the multiple copies may be used to enhancereliability of the storage device in that damage to one recordable mediasurface or its corresponding read/write head need not preclude ongoingoperation of the dynamically mapped storage device since another copymay be available on a different rotating recordable media surface withits corresponding different read/write head assembly. Further, those ofordinary skill in the art will readily recognize that any combination ofthese various physical locations may be combined to provide bothenhanced performance and reliability. In other words, additional copiesof host supplied data may be positioned at different rotationalpositions of a single track, at different radial track positions of thesame recordable surface, and/or on different recordable surfaces of thestorage device. Any combination of these various positioning options maybe employed to enhance both performance and reliability of thedynamically mapped storage system.

FIG. 23 is a block diagram depicting exemplary functional elementswithin disk controller 106 useful in providing multiple indirections(multiple copies) in accordance with features and aspects hereof. Asnoted above, disk controller 106 may include indirect logical tophysical mapping element 108 generally responsible for the dynamicallymapped features of the storage device. An aspect of the logical tophysical mapping element 108 as noted above may include a dataduplicator element 2300 operable to provide a mapping of multiple copiesof host supplied data (e.g., multiple indirections in the logical tophysical mapping structures for any particular host supplied logicalblock of data). Data duplicator element 2300 may include variouselements to analyze operation of the dynamically mapped storage deviceto determine how many copies to generate for host supplied data andwhere to position such multiple copies in the physical address space ofthe dynamically mapped storage device.

Operating parameters analyzer 2304 may be operable to analyze variousoperating parameters of the dynamically mapped storage device to detectpotential reliability issues in the operation of the dynamically mappedstorage device. Exemplary of such operating parameters are the operatingtemperature of the storage device (e.g., temperature of the read/writehead assembly), the current bit error rate for read operations performedon the storage device, shock and vibration event rates for the storagedevice, etc. These and other operating parameters are easily detected byoperation of disk controller 106 as well known to those of ordinaryskill in the art. The monitored operating parameters may be analyzed byoperating parameters analyzer 2304 to detect the possible onset ofreliability problems in the dynamically mapped storage device. Dataduplicator element 2300 cooperates with operating parameters analyzer2304 to determine when the number of duplicate copies of host supplieddata should be increased due to detection or onset of possiblereliability problems or may be decreased if the storage device isoperating well within normal operating parameter ranges. Normal rangesare unique to each particular application of features and aspects hereofand would be readily understood by those of ordinary skill in the art.

In addition, data duplicator element 2300 may include capacity analyzerelement 2306 for analyzing the current capacity ratio. The “currentcapacity ratio”, as used herein, is defined generally as the total sizeof all host supplied logical data blocks presently stored on the storagedevice divided by the total size of the physical space of the storagedevice. As the current capacity ratio increases, less space may beavailable for storing duplicate copies of host supplied the logicalblocks of data. For example, if current operating conditions of thedynamically mapped storage device suggest that two copies of eachlogical block may be stored on the mapped logical drive, as the currentcapacity ratio approaches 0.5, there may be insufficient space tocontinue storing such a duplicate copy of each logical block. In otherwords, a host system has stored logical blocks totaling about half thespecified capacity of the storage device. But, since each block isduplicated, the total capacity of the storage device may be filled.However, while the current capacity ratio is well below 0.5, processingon the logical mapped storage device may continue to duplicate eachlogical block in the physical storage space of the storage device. Thus,capacity analyzer 2306 continually monitors the current capacity ratioto determine when fewer (or no) duplicate copies may be stored on thestorage device.

Critical data analyzer 2308 within data duplicator 2300 is operable toanalyze host supplied logical blocks of data to identify those that maylikely contain data to be considered “critical” in this particularapplication. For example, inode or FAT file system structures may bedeemed critical in the information stored on a storage device in thatthey define the entire file structure of a file system stored on thestorage device. Thus, such data structures may be considered “critical”.Critical data analyzer 2308 may apply heuristic rules to make suchdeterminations of criticality by observing the logical block usage ofthe host system and/or by observing the host supplied data for certainsignature characteristics. Or, for example, certain data in particularapplications may be designated by the host systems as sensitive andhence critical. Critical data, however it is detected or designated, mayreceive preferential treatment in disk controller 106 such that criticaldata will be duplicated more frequently than non-critical data. Thus,critical data analyzer 2308 is generally operable to help identify suchcritical data to assure that any duplication of data emphasizesduplication of critical data over non-critical data. Where the hostsystem defines the critical nature of particular data, critical dataanalyzer 2308 may interact with a host system driver to receive specialdirectives indicating logical block ranges that may be deemed critical.Or, for example, a write request received from a host system may simplyinclude parameters indicating that the data to be written is deemedcritical by the host application.

Duplicate block remover element 2302 within data duplicator 2300 isgenerally operable to identify duplicate copies of logical blocks thatmay be removed responsive to a need identified in the storage device toreduce the number of duplicate blocks. For example, as current capacityanalyzer 2306 detects the current capacity ratio approaching orexceeding 0.5, it may direct duplicate block remover 2302 to identifyduplicate blocks that may be removed to make room for more host supplieddata. Duplicate block remover element 2302 may, for example, identifyduplicate blocks for non-critical data that may be removed to increasethe amount of physical space available on the storage device and hencereduce the current capacity ratio. Or, for example, duplicate blockremover element 2302 may identify additional duplicate blocks above andbeyond a single duplication (e.g., more than 2 copies of a host suppliedblock). Additional copies may be removed to increase physical capacityof the storage device relative to the logically stored content (e.g., toincrease the current capacity ratio).

Those of ordinary skill in the art will readily recognize that thevarious functional elements 2300 through 2308 shown as operable withinthe indirect logical to physical mapping element 108 of controller 106may be combined into fewer discrete elements or may be broken up into alarger number of discrete functional elements as a matter of designchoice. Thus, the particular functional decomposition suggested by FIG.23 is intended merely as exemplary of one possible functionaldecomposition of elements within controller 106.

FIG. 24 describes related methods in accordance with features andaspects hereof to create and write multiple copies (multipleindirections) of host supplied logical blocks of data and to select oneof the multiple copies for return of requested data to a host system. Ingeneral, elements 2400 through 2404 represent processing of thedynamically mapped storage device responsive to receipt of a writerequest from an attached host system. As noted above, the host systemsupplies one or more logical blocks of data with a write request.Logical to physical mapping features and aspects hereof then map thesupplied logical blocks to physical storage space of the mapped storagesystem. In addition, the mapping features generate multiple copies inaccordance with current operating parameters and other aspects of thestorage device. Each of the multiple copies is mapped to physicallocations using the same host supplied logical block address.

Those of ordinary skill in the art will recognize the integration offeatures of FIG. 24 with the general read and write processing of FIG.11 above. In general, elements 2400 through 2404 are operable to writeone or more copies of a supplied logical block to corresponding one ormore physical locations. Processing of FIG. 11 shows the detailsinvolved in writing each of the multiple copies.

In particular, element 2400 is first operable to receive a write requestfrom the attached host system providing one or more logical blocks ofdata to be stored on the dynamically mapped storage device. Transparentto the host system, element 2402 within the dynamically mapped storagedevice may then determine a number of copies of the supplied logicaldata blocks to be written in the physical storage space of thedynamically mapped storage device. At least one copy will be mapped tocorresponding physical blocks and stored in the storage device. Zero ormore additional copies of the supplied data may then be written tocorresponding physical locations and mapped to the same supplied logicalblock address. As noted above and as discussed further herein below,numerous factors may be involved in the decision as to how many copiesof the supplied logical blocks should be recorded in the physicalstorage space of storage device. Element 2404 is then operable to writea first copy of the supplied data and zero or more additional copies ofthe received logical blocks in corresponding physical locations of thedynamically mapped storage device. Each copy written is also mapped byan entry in the mapping tables pointing the supplied logical blockaddress to the various physical copies stored in the storage devicemedia. As noted above and as discussed further herein below, otherprocessing may determine optimal physical locations for each of themultiple copies to improve reliability of the dynamically mapped storagedevice and/or performance of the dynamically mapped storage device. Alsoas noted above, details of the processing involved in writing each ofthe one or more copies of the host supplied logical data blocks isprovided above in the description of FIG. 11. In particular, multipleadjacent physical blocks written to a cache memory are coalesced into alarger frame structure eventually posted to the recordable media of thestorage device.

Elements 2410 through 2414 generally represent processing within thecontroller of the dynamically mapped storage device responsive toreceipt of a read request from an attached host system. In general, anattached host system requests return of identified blocks of dataidentified by the logical block addresses previously supplied in a hostsystem write request. As noted above, logical to physical mappingfeatures and aspects hereof then determine where each of potentiallymultiple copies of the supplied data has been recorded on the physicalstorage space of the dynamically mapped storage device. Similar mappingprocesses are then used to determine the physical location of one ormore of the various mapped copies of the identified logical blocks. Morespecifically, element 2410 is first operable to receive a read requestfrom an attached host system indicating one or more logical blockaddresses to be retrieved and returned to the requesting host. Element2412 is then operable to select one of the one or more mapped copies ofthe identified logical blocks. As noted above, in performing thecorresponding write request, one or more duplicate copies of thesupplied logical blocks of data have been recorded in the dynamicallymapped storage device at different physical locations but all mapped tothe same logical block address. Element 2412 is therefore operable toselect a preferred one of the one or more duplicate copies of theidentified data. As noted above and as discussed further herein below,certain copies may be preferred based upon enhanced reliability of thestorage device and/or based upon enhanced improvement enhancedperformance of the storage device. Having so selected one of the one ormore mapped copies, element 2414 is then operable to return therequested data from the selected copy stored in the physical storagespace of the dynamically mapped storage device.

As above with respect to elements 2400 through 2404, details of theprocessing involved in reading particular identified logical blocks fromtheir corresponding physical locations are provided above with respectto FIG. 11. Thus a selected copy of the identified information is readas one or more physical frames and any extraneous leading or trailingdata is trimmed and discarded.

Further details of the processing to write and read multiple copies ofhost supplied data are presented further herein below with reference toadditional figures. The processing of the methods of FIG. 24 aretherefore intended as suggestive of the broad enhancements in accordancewith features and aspects hereof to provide multiple copies of hostsupplied data using the logical to physical mapping features and aspectshereof.

FIG. 25 is a flowchart describing a method in accordance with featuresand aspects hereof to monitor operational parameters and the currentcapacity ratio of the storage device to determine when previouslyrecorded copies of logical host supplied logical data may be removed. Asnoted above, various operational parameters of the storage device mayindicate that various failure modes may be more or less likely to occursoon. For example, as the operating temperature of the storage device(e.g., the temperature of the read/write head assembly per se) increasesbeyond certain identified thresholds, various failures in the recordingand/or reading of data may start to occur. Or, for example, as the biterror rate in read operations increases failures may be more prevalent.Or, for example, as the shock and vibration detected events increasefailure may be imminent. Element 2500 is therefore operable to monitorthese and other operating parameters as well as the current capacityratio to help determine when duplicate copies of stored host supplieddata may be removed. For example, when the operational parametersindicate that the storage device is operating within normal operatingparameter ranges such that failures are less likely, additionalduplicate copies of data may be removed. Conversely, where operationalparameters indicate the possibility of imminent failure, additionalcopies of host supplied data may be recorded to help preclude loss ofdata should such a failure occur. As the operating parameters come backwithin the normal range, the additional duplicate copies could beremoved thereby improving the current capacity ratio. In addition,regardless of the current operating parameters, as the current capacityratio reaches or exceeds 0.5, it may be beneficial to remove additionalduplicates of information to allow the full physical capacity of thestorage device to be utilized.

Responsive to the monitored information from element 2500, element 2502is next operable to determine whether the monitored informationindicates that additional duplicate copies of previously stored datashould be removed. If not, processing continues looping back to element2500 to continue monitoring operating parameters and current capacityratio. If previously stored copies may or must be removed, element 2504is next operable to select particular duplicate copies of previouslyrecorded data for removal and to remove such data by simply eliminatingthe duplicated mapping information in the mapping tables of the storagesystem storage device. As noted above, when each duplicate copy iswritten to corresponding physical space of the storage device, a mappingtable entry reflects the duplicate mapping of the supplied logical blockaddress to the additional duplicate physical storage space. Thus,removal of a previously stored duplicate of host supplied data mayentail simply removing the duplicate mapping table entries thus freeingthe corresponding physical storage space for other use in the storagedevice. Processing then continues looking back to element 2500 tocontinuously monitor the operating parameters and current capacityratio. Thus, the method of FIG. 25 may be operable as a backgroundprocessing task within the controller of the storage device.

FIG. 26 is a flowchart providing additional exemplary details of element2402 discussed above with respect to FIG. 24. As noted above, element2402 of FIG. 24 is operable to determine a number of additional copiesof host supplied data to be written to the physical storage space of thedynamically mapped storage device. Element 2600 is first operable toinitialize a copy count “N” to a value of 1 (i.e., presuming noadditional copies of data are to be written). Element 2602 is thenoperable to analyze current operating parameters including, as notedabove, operating temperature, bit error rate, shock and vibration eventfrequency, etc. Element 2604 is then operable to determine from theanalysis of element 2602 whether the probability of failure of thestorage device is higher or lower. If element 2604 determines that theprobability of failure is relatively high, element 2606 is next operableto increase the value of N to indicate that more copies of the supplieddata would be desirable. N may be increased incrementally or by anyvalues but typically not beyond some predetermined maximum value.Element 2608 is then operable to determine the current capacity ratio.As noted above, the current capacity ratio may be determined as thetotal size of all host supplied logical blocks divided by the totalphysical space of the mass storage device. Element 2610 then determineswhether the current capacity ratio is nearing or exceeds about 0.5. Ifso, element 2612 is operable to decrease N so that fewer duplicatecopies will be recorded and hence slow the increase of the currentcapacity ratio. N may be decreased incrementally or by any amount buttypically not below a minimum of 1 (e.g., at least one copy must bewritten responsive to a host system write request). Element 2614 is thenoperable to determine if the host supplied data to be written isconsidered “critical”. As noted above, data may be designated as“critical” by interaction with the host system through parameters of thewrite request or other control sequences unique to the particular hostsystem. Or, for example, logical blocks may be determined to be“critical” by application of heuristic rules within the dynamicallymapped storage device. For example, the dynamically mapped storagedevice may heuristically identify a particular range of logical blockaddresses typically used for the FAT or inode file system datastructures. Or, for example, the storage device may recognize particularsequences of data as typical of such structures or otherwise detect datato be deemed critical in this application. However the criticality ofthe host supplied data is determined, element 2616 is operable todetermine whether the current data has been so identified as critical.If so, element 2618 is operable to increase N so that additionalduplicates of the data to be written should be recorded on the physicalstorage space of the dynamically mapped storage device.

FIG. 27 is a flowchart providing exemplary additional details of theoperation of element 2404 as described above in FIG. 24. Element 2404 asnoted above is generally operable to write one or more copies (N copiesas determined above) of the host supplied data at corresponding physicallocations of the dynamically mapped storage device. As noted above, eachcopy of the host supplied data is associated with a correspondingmapping table entry mapping the same logical block address to each ofthe one or more copies in the physical address space of the storagedevice. Specifically, element 2700 of FIG. 27 is first operable todetermine how to best distribute the one or more copies of the hostsupplied data over corresponding multiple rotational positions of aparticular track, and/or over multiple radial track positions, and/orover multiple read/write heads (e.g., multiple recording surfaces of thestorage device). As noted above, the distribution of such multiplecopies may be determined in a manner to enhance reliability of thedynamically mapped storage device and/or performance of the dynamicallymapped storage device. For example, distributing duplicate copies atmultiple radial tracks locations dispersed between inner diameter radialpositions and outer diameter radial positions may aid in eitherperformance enhancement or reliability enhancement. Similarly, recordingmultiple copies at different rotational positions of the same track mayalso enhance either reliability or performance. Still further, recordingmultiple copies on different read/write heads (e.g., on differentrecording surfaces of the storage device) may enhance either reliabilityor performance. Reliability may be enhanced by selecting multiplelocations that may help avoid physical damage to a particular area ofthe recordable media of storage device and/or may avoid failure of aparticular read/write head. Selecting the multiple locations forrecording multiple copies may enhance performance by distributing themultiple copies such that when the logical blocks are to be read back toa requesting host system, the most rapidly accessible copy may bereturned to the requesting host system. For example, if the read/writehead is already positioned at the proper radial track, the next copy tobe encountered in the rotation of the storage media may be returned tothe host system. Or, for example, where the read/write head is notpresently positioned at an appropriate radial track position, the mostrapidly accessible radial track position having a copy of the requesteddata may be used for return of the requested logical blocks.

Having so identified one or more possible distributed locations in thephysical address space of the dynamically mapped storage device, element2702 is next operable to determine whether the current operatingparameters indicate a possible failure associated with one or more ofthe identified, distributed physical locations. If current operatingparameters of the dynamically mapped storage device indicate that one ormore of the identified, distributed physical locations may be associatedwith a likely imminent failure of the storage device, element 2704 isoperable to relocate the selected mapping of one or more of the variousduplicate copies to reduce the probability of data loss from an imminentfailure. Lastly, element 2706 is next operable to write the hostsupplied logical blocks and any desired multiple copies thereof to thecorresponding mapped physical space of the dynamically mapped storagedevice. As noted above, writing the data to the physical storage spacealso includes generating appropriate mapping table entries to associatethe host supplied logical block addresses with each of the multiplecopies stored in the physical space of the storage device.

FIG. 28 is a flowchart providing additional exemplary additional detailsof the operation of element 2412 of FIG. 24. As noted above, element2412 of FIG. 24 is generally operable to select one of the one or morecopies of an identified logical block address previously stored in thestorage device for return to the requesting host system (e.g., inresponse to a read request from the host system). Element 2800 of FIG.28 is first operable to select one of the one or more duplicates of theidentified logical block addresses. Preferably, the selected copy isthat which is determined to be most quickly accessed by the storagedevice. For example, if the read/write head is presently positioned atthe proper radial track position, the copy of the requested data thatwill be next encountered as the storage media continues to rotate underthe read/write head will be selected for return to the requesting hostsystem. Or, for example, if the read/write head is not presentlypositioned at a radial track position that contains one of the one ormore duplicate copies, the closest or most rapidly accessible radialtrack position that does contain one of the one or more duplicate copiesmay be next accessed. Next element 2802 determines whether theidentified selected copy is one which the current operating parametersindicate may be subject to an imminent failure. If so, element 2804 isoperable to select a different copy of the one or more duplicates of theidentified logical block addresses, preferably a copy less likely toencounter data loss from a potential imminent failure. Lastly, element2806 is operable to return the requested data from the selected copy ofthe one or more duplicate copies of the identified logical blocks.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 24 through 28 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to permitting generation of multiple indirection table entriesfor any user data written to the recordable media of the dynamicallymapped storage device. Numerous equivalent methods and techniques willbe readily apparent to those of ordinary skill in the art to implementsuch features as a matter of design choice.

Dynamic Recording Density Control

It remains an ongoing problem in all storage devices to improvereliability and performance of the storage device. To improvereliability of data stored on the disk drive, it may be desirable torecord data at lower densities on the recordable media. However, lowerdensity recordings reduce the capacity of the disk drive. Present daydisk drives typically do not permit dynamic recording of data on therecordable media. Thus, all data must be recorded at the same density.

Since all user data written to the dynamically mapped storage device isdynamically mapped from the user supplied logical address space (logicalblock addresses or LBAs) to the physical disk block address space (diskblock addresses or DBAs—blocks of variable, independent size relative tothe LBA size), features and aspects hereof permit varying of therecording density for host supplied data written to the storage devicerecordable media. In general, most disk drive applications rarely usethe entire capacity of a storage device. Since the mapping features andaspects hereof permit independence and separation of logical block sizesfrom the variable physical block sizes, recording densities may bealtered while the utilization of the recordable media is lower (e.g.,lower than a threshold value). In general, so long as the currentcapacity utilization as represented by a current capacity ratio (asdiscussed above) is below a threshold value, new data recorded to therecordable media of the storage device may be recorded at a lowerdensity.

In one aspect, the track density may be decreased (e.g., track pitch maybe increased). In addition or in the alternative, the longitudinal orbit density may be varied such that new data recorded to the dynamicallymapped storage device may be recorded at a lower bit density. Byreducing the storage density (e.g., radial track density and/orlongitudinal or bit density), the dynamically mapped storage device mayoperate at a lower error rate compared to storage devices devoid of thedynamic density control features and aspects hereof. Reduced trackdensity, though decreasing available physical capacity, enhancesreliability by reducing potential interference from signals on adjacenttracks. Those of ordinary skill in the art will readily recognizepractical limits on the reduction of track density. Typical present daystorage devices rely on some degree of overlap of the recorded tracksignals to permit rapid detection of “off track” conditions. Thus,although features and aspects hereof permit some reduction in trackdensity to enhance reliability of the stored data, beyond some readilydetermined threshold further reduction may be counterproductive in thatoff track conditions may be missed. The particular threshold for anyspecific storage device application will be readily determined by thoseof ordinary skill and the art in accordance with parameters of theparticular storage media, the particular read/write head assembly, thehead flying height, and numerous other factors.

In addition, features and aspects hereof provide for dynamic adjustmentto the longitudinal or bit density for purposes of improving reliabilitywhere unused storage capacity is available in the dynamically mappedstorage device. As discussed above in detail, the dynamically mappedstorage device may preferably write physical disk blocks aggregated orcoalesced into a meta-structure referred to herein as a frame containingone or more physical disk blocks. When written to the recordable media,frames may be recorded using a lower bit density to improve readabilityof the data (e.g., the read/write head flying height may be increased).

The mapping table entries used to map logical block addresses into oneor more physical disk block addresses may include metadata indicatingthe present recording density for the frame in which the physical datablocks are stored. Thus, features and aspects hereof may inquire of themapping table entries to determine the present recording density for anyidentified portion of data recorded on the storage device.

The recordable media of the storage device may be subdivided into zonesof varying recording density. In a simple implementation, two types ofzones may be defined. One or more normal density zones may be definedwherein track density and bit density are set in accordance with normalspecification of the storage device. Zero or more low density zones maybe defined wherein track density and/or bit density are reduced toimprove reliability in the reading of that data.

The number and types of the zones may be dynamically determined by thecontroller of the storage device. The number, types, and physicallocation of defined zones may be determined dynamically as a function ofthe current capacity ratio and/or any of various operating parameters ofthe storage device. Numerous conditions may be monitored to determinewhen reliability of the storage device may be enhanced in accordancewith dynamic density control features and aspects hereof. For example,the current physical capacity utilization represented by the currentcapacity ratio as discussed above may be a first factor in determiningwhether it is presently feasible to reduce the recording density fornewly written data.

When write requests are processed, data may be recorded in a normaldensity zone or in a low density zone. In particular, data identified as“critical” may be recorded in a low density zone to improve reliabilityof reading the data. Host interaction or other heuristic rules may beapplied to identify host supplied data likely to be critical tooperation of the host system. For example, FAT or inode file system datastructures may be deemed critical and may often be detected either byrecognizing particular ranges of logical block addresses utilized by thehost system and/or recognized by detecting certain signature datapatterns likely to represent such file system data structures. As above,those of ordinary skill in the art will readily recognize numerous othertechniques for recognizing “critical data” including, for example,receiving directives from the host system indicating that identifieddata is to be deemed critical (e.g., directives in the form ofspecialized control sequences or in the form of parameters associatedwith write requests). Data so identified as critical may be written(physical capacity permitting) with lower density so as to aid inreducing the possibility of failure when reading such critical datarecorded at a lower recording density.

Still further, as discussed herein below, operational parameters of thestorage device and in particular operational parameters of particularread/write head assemblies may be monitored to define reduced densityzones associated with a particular read/write head. This may includemonitoring a Bit Error Rate (BER) and an Off track read capability(OTRC) to determine if a particular head should be used in a lessstressful manner.

FIG. 29 is a block diagram depicting exemplary functional elementswithin disk controller 106 useful in providing dynamic recording densitycontrol in accordance with features and aspects hereof. As noted above,disk controller 106 may include indirect logical to physical mappingelement 108 generally responsible for dynamic mapping features of thestorage device. An aspect of the logical to physical mapping element 108as noted above may include a density control element 2900 operable toprovide dynamic control over the density of information written to therecordable media and later read therefrom. Density control element 2900may include various elements to analyze operation of the dynamicallymapped storage device to determine when and how to modify the recordingdensity of information written to and read from the physical addressspace of the dynamically mapped storage device.

Operating parameters analyzer 2904 may be operable to analyze variousoperating parameters of the dynamically mapped storage device to detectpotential reliability issues in the operation of the dynamically mappedstorage device. Exemplary of such operating parameters are the operatingtemperature of the storage device (e.g., temperature of the read/writehead assembly), the current bit error rate for read operations performedon the storage device, shock and vibration event rates for the storagedevice, as well as operating parameters specific to each read/write headassembly such as read bias and flying height. These and other operatingparameters are easily detected by operation of disk controller 106 aswell known to those of ordinary skill in the art. The monitoredoperating parameters may be analyzed by operating parameters analyzer2904 to detect the possible onset of reliability problems in thedynamically mapped storage device. Density control element 2900cooperates with operating parameters analyzer 2904 to help define moreor fewer reduced density zones on the recording surface as may besuggested by the current operating parameters. The number of reduceddensity zones may be increased when the operating parameters indicateoperation outside a normal range such that failures may be more common.Conversely, the number of reduced density zones may be decreased whenthe operating parameters are within a normal range. “Normal ranges” areunique to each particular application of features and aspects hereof andwould be readily understood and determined for any particularapplication by those of ordinary skill in the art.

In addition, density control element 2900 may include capacity analyzerelement 2906 for analyzing the current capacity ratio (as definedabove). As the current capacity ratio increases, less space may beavailable for recording at lower than nominal or normal recordingdensity. Since the storage device will be specified to store aparticular maximum physical capacity, the ability to record data atlower than normal or nominal density may not be available as thephysical storage space is temporarily reduced defining more zones asused for reduced density recording. For example, as the current capacityratio approaches, for example, 0.5, there may be insufficient space tocontinue storing such lower density recordings of host supplied data.

In other words, a host system has stored logical blocks totaling abouthalf the specified capacity of the storage device. But, since manyblocks may be recorded at a lower than normal density, the totalcapacity of the storage device may be nearly filled. However, while thecurrent capacity ratio is well below 0.5, processing on the logicalmapped storage device may continue to record information at reduceddensity. Thus, capacity analyzer 2906 continually monitors the currentcapacity ratio to determine when to discontinue storing data at reduceddensity (as well as when to start migrating information back to normalor nominal density to thereby restore available physical storage spaceon the storage device).

Critical data analyzer 2908 within data duplicator 2900 is operable toanalyze host supplied logical blocks of data to identify those that maylikely contain data to be considered “critical” in this particularapplication. For example, inode or FAT file system structures may bedeemed critical in the information stored on a storage device in thatthey define the entire file structure of a file system stored on thestorage device. Critical data analyzer 2908 may apply heuristic rules tomake such determinations of criticality by observing the logical blockusage of the host system and/or by observing the host supplied data forcertain signature characteristics. Or, for example, certain data inparticular applications may be designated by the host systems assensitive and hence critical. Critical data, however it is detected ordesignated, may receive preferential treatment in disk controller 106such that critical data will be recorded at a lower density than is usedfor non-critical data. Thus, critical data analyzer 2908 is generallyoperable to help identify such critical data to assure that any enhancedreliability from reduced recording density emphasizes reliability ofcritical data over non-critical data. Where the host system defines thecritical nature of particular data, critical data analyzer 2908 mayinteract with a host system driver to receive a special directiveindicating logical block ranges that may be deemed critical. Or, forexample, a write request received from a host system may simply includeparameters indicating that the data to be written is deemed critical bythe host application.

Density migration element 2902 within density control element 2900 isgenerally operable to identify information recorded in a lower densityzone that may be migrated or re-recorded in a normal recording densityzone—or vice versa. Migrating previously recorded data to a normaldensity zone frees more physical space for re-use. For example, ascurrent capacity analyzer 2906 detects the current capacity ratioapproaching or exceeding 0.5, it may direct density migration element2902 to identify low density zones containing data that may be migratedto a normal density zone. Such a migration of previously recordedinformation from low density zones to normal density zones restoresphysical space that may be used to store additional data up to thespecified capacity of the storage device. Conversely, migratingpreviously recorded information from normal density zones to low densityzones reduces the physical capacity of the storage device below itsspecified capacity and hence increases the current capacity ratio.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 2900 through 2908 shown as operable withinthe indirect logical to physical mapping element 108 of controller 106may be combined into fewer discrete elements or may be broken up into alarger number of discrete functional elements as a matter of designchoice. Thus, the particular functional decomposition suggested by FIG.29 is intended merely as exemplary of one possible functionaldecomposition of elements within controller 106.

FIG. 30 is a schematic representation of a single surface of a rotatingdisk recordable media. The recordable media surface 3000 comprises aplurality of concentric tracks logically laid out from an inner diameterthrough an outer diameter. In accordance with the dynamic densitycontrol features and aspects hereof, the concentric tracks are groupedin zones of varying density. Zones “A” and “C” are lower recordingdensity zones while zones “B” and “D” are nominal or standard recordingdensity zones. As noted above, the density may be varied in the radialtrack pitch and/or in the longitudinal bit recording density. Zones Aand C are shown as containing less information e.g., lower recordingdensity (track density, bit density, or both) as compared to normalrecording density of zones B and D. Physical blocks (e.g., within aframe) 3002 in zone C (a lower density zone) is shown as recorded usingphysically more space than frame 3004 recorded in zone B (a normaldensity zone). Those of ordinary skill in the art will readily recognizethat the scale of elements of FIG. 30 are not intended to preciselyreflect radial or longitudinal density or spacing nor even the typicallayout of tracks or surfaces in any particular storage device. Rather,the Figure is intended merely to suggest the dynamic density featuresand aspects hereof wherein data may be dynamically recorded in a reducedrecording density zone or in a normal recording density zone in responseto current operational status of the storage device and/or in responseto current capacity ratio determinations.

As will be discussed further herein below, a lower density recordingzone may be converted or migrated back to a normal recording densityzone where utilization of the physical capacity of the storage devicestarts to rise. Typically the physical capacity of the storage device isspecified presuming the recording density to be static rather thandynamically reduced in accordance with features and aspects hereof. Thusas the physical capacity of the storage device starts to fill, datarecorded in a reduced density zone may be migrated into a normalrecording density zone and the reduced density zone may be reconfiguredas a normal recording density zone.

Not shown in FIG. 30 but readily apparent to those of ordinary skilledin the art is a structure wherein each of multiple surfaces of a storagedevice may be so controlled for dynamic density recording. Thus eachsurface may be configured with some number of normal recording densityzones and some number of reduced density recording zones. Still further,in another aspect, particular surfaces may be configured with reducedrecording density zones either in part or in their entirety while othersurfaces may be configured exclusively for normal density recording. Anentire recording surface may be selected for reduced density recordingbased upon operating parameters of the read/write head assemblyassociated with the head. Those of ordinary skill in the art willreadily recognize that normal and lower density zone may be distributedover the recordable media surfaces of the storage device in any ofseveral configurations in accordance with the needs of a particularapplication.

FIG. 31 is a block diagram similar to FIG. 20 described above. FIG. 31schematically represents adjacent written tracks using such a read/writehead configuration that, in conjunction with mapping features andaspects hereof, permits variable track density. Tracks 3110 and 3112 arewritten in a normal recording density zone with a nominal track pitch3102 (a track pitch less than the write head width 3000). By contrast,tracks 3114 and 3116 represent tracks written in low density zone with alower or reduced track density (e.g., a wider track pitch 3104). Eachtrack 3110, 3112, 3114, and 3116 has a track centerline indicated by acorresponding thicker dashed line. In accordance with variable densityfeatures and aspects hereof, tracks 3110 and 3112 are written at nominaltrack pitch 3102. However, tracks 3114 and 3116 are further offset byreducing track density and thus have an increased track pitch 3004(i.e., a reduced track density).

As noted above, reducing track density (by increasing track pitch) canoffer diminishing returns if the track pitch is too large. Proximity ofinformation from an adjacent track is an aspect of sensing “off track”conditions in most present day disk drives and is used for controllingand correcting the flight of the read/write head over the trackcenterline. The track pitch shown in FIG. 31 is not intended to expressany precise dimensions of actual track pitch values or even a relativescale of normal versus low track density. Rather, the increased trackpitch 3104 is intended only as suggestive of the ability to increasetrack pitch (reduce track density) relying upon the mapping features andaspects hereof in which logical to physical mapping allows separationand independence of the logical block addresses and sizes and thephysical block addresses and sizes.

FIGS. 32 and 33 are schematic representations of a frame (containing oneor more physical disk blocks) as described above in accordance with themapping features and aspects hereof. FIG. 32 represents a frame writtenin nominal longitudinal or bit density while FIG. 33 represents the sameframe written with reduced bit density in accordance with features andaspects hereof. The frame of FIG. 32 includes a preamble field 3200, async field 3202, a data field 3204, and an ECC (error correction) field3206. Identical fields are present in the frame of FIG. 33 butrepresented graphically as longer suggesting the lower recording densityof the frame. In particular, preamble field 3300, sync field 3302, datafield 3304, and ECC (error correction) field 3306 are each shown asstretched in the longitudinal direction of recording relative to thecorresponding fields of FIG. 32. As above, FIGS. 32 and 33 are notintended to represent any particular or even accurate scale of the sizeof a recorded frame. Rather, FIGS. 32 and 33 are merely intended tosuggest the reduction of longitudinal or bit density of a recorded blockor frame in accordance with the dynamic density control features andaspects hereof.

A normal density frame of FIG. 32 is written in a normal density zone ofthe storage device while a lower density frame of FIG. 33 is written ina low density zone of the storage device. A block or frame may bemigrated or re-recorded from a normal (higher) density zone to a lowerdensity zone to improve reliability in reading of the data. Conversely,a block or frame may be migrated or re-recorded from a lower or reduceddensity zone back to a normal or nominal density zone as the physicalcapacity of the storage device starts to fill.

Features and aspects hereof include selecting an appropriate densityzone for writing of host supplied logical blocks. FIG. 11 discussedabove represents the processing of such a write request in accordancewith the logical to physical mapping features and aspects hereof. Ingeneral as expressed in FIG. 11 and support descriptions above,processing of a write request includes locating consecutive physicaldisk blocks to which the host supplied logical block addresses may bemapped. Appropriate mapping table entries are generated and the hostsupplied data is transferred to the selected physical block addresses.The transfer to physical block addresses may involve buffering orcaching so that multiple physical disk block writes may be coalesced oraggregated to a larger frame construct that better utilizes processingand data transfer bandwidth of the storage device controller.

In particular, element 1126 of FIG. 11 above represents processing tolocate appropriate contiguous physical blocks to which the host suppliedlogical blocks are transferred and mapped. FIG. 34 is a flowchartproviding additional exemplary details of the processing of element 1126to select physical blocks in an appropriate density zone as defined inaccordance with features and aspects hereof Element of 3400 is firstoperable to determine whether any low density recording zones arepresently configured on the recordable media of the dynamically mappedstorage device. If not, processing continues and element 3408 asdiscussed further here and below. If so, element 3402 is next operableto determine whether the host supplied logical blocks of data mayrepresent critical data. As noted above, critical data may include datadeemed to be critical to the host system either by heuristic analysis ofthe storage device performed by the storage device or as directlyidentified by modified host applications using specialized controlsequences or parameters in the write requests. If element 3402determines that the host supplied logical block data does not includecritical data, processing continues with element 3408 as discussedherein below. If the method determines that the logical blocks mayrepresent critical data, element 3404 is next operable to attempt tolocate unused contiguous physical disk space in a reduced density zoneof the storage device recordable media. Although tests have alreadyconfirmed that some low density recording zones are presentlyconfigured, there may or may not be enough space in such low densityrecordings zones to record the presently supplied host data. Element3406 then determines whether sufficient space has been located in anappropriate low re-recording density zone. If so, processing of themethod completes and remaining processing described above with respectto FIG. 11 completes processing of the write request. Otherwise,processing continues with element 3408.

If there is insufficient space in any low re-recording density zone orif the host supplied data is deemed non-critical, element 3408 is nextoperable to attempt to locate sufficient unused contiguous physical diskspace within one or more of the normal recording density zones of thedynamically mapped storage device. Element 3410 is then operable todetermine whether sufficient physical space was so located. Ifsufficient space is located by operation of element 3408, processing ofelement 1126 is completed and further processing of FIG. 11 describedabove completes the host write request. If insufficient space ispresently available in the normal recording density zones of the storagedevice, element 3412 is operable to await an increase in the physicalcapacity as may be generated by background processing described furtherherein below. As noted above, various monitor processing (e.g.,background processes) within the storage device controller mayperiodically migrate information from low density to normal density orvice versa as may be required to better utilize the specified physicalcapacity of the storage device. For example, where the current capacityratio starts to rise significantly, background processing may be invokedto migrate data from low density zones to normal recording density zonesto thereby free the physical space comprising a low density zone forre-use. The freed low density zone may then be re-configured for re-useas a normal recording density zone thereby increasing the availablephysical capacity of the storage device. Eventually, sufficient physicalcapacity will be restored to permit storage of the data in the presenthost write request. If the physical capacity of the storage device iscompletely filled with all recording zones configured for normalrecording density, standard error processing (well known to those ofordinary skill in the art) is invoked to so indicate the erroneousrequest to a user. When element 3412 detects some increase in thephysical capacity, processing continues looping back to element 3400 torepeat the search to locate sufficient physical disk space either in anyremaining low density zones or the presently defined normal densityzones of the storage device.

Those of ordinary skill in the art will readily recognize that a varietyof other factors may be utilized to determine whether a particular hostwrite request should be stored in a low density zone or a normal densityzone. Further, a variety of density zones may be defined rather thansimply two levels of recording density—a normal recording density and asingle lower recording density. Those of ordinary skill in the art willrecognize that a variety of useful intermediate density recording zonesmay be defined. Thus, processing of FIG. 34 is intended merely asexemplary of one possible embodiment of features and aspects hereofwherein a variety of different recording density zones may be definedand selected based on any of several criteria associated with aparticular host write request.

Further, those of ordinary skill in the art will readily recognize thatthe read and write request processing of FIG. 11 may be triviallymodified to include appropriate reprogramming of read/write head densitycontrol parameters to successfully complete a particular read or writerequest. In particular, referring again to FIG. 11, read requestprocessing element 1108 may include suitable programming of servocontrols and other control mechanisms to properly adapt the read/writehead for reading information in accordance with the density requirementsof the particular zone storing the requested host data. In like manner,element 1132 includes suitable programming of read/write head parametersand other operational parameters to properly record the data inaccordance with density specifications of the associated zone.

FIG. 35 is a flowchart representing exemplary background processing tomonitor various aspects of the operating storage device. Responsive tothe monitored information, the method is also operable to migrateinformation between low and normal recording density zones and toreconfigure the number of such zones as appropriate for the currentoperating parameters of the storage device. Element 3500 is firstoperable to measure or monitor various current operating parameters ofthe storage device including, for example, the current capacity ratio.As noted above, numerous other operating parameters may be monitored anduseful to reflect the reliability of the storage device and hence theneed for more or less low recording density zones. Element 3502 thendetects from the currently measured parameters and capacity whether itis appropriate to reduce the number of lower density recording zones tothereby restore physical capacity for storage of additional data. Asnoted above, defining a zone for low density recording decreases theavailable physical space on the storage device below that of the normalspecifications of the storage device. Thus, as the storage device fills,the number of low recording density zones may need to be reduced toachieve the specified physical capacity of the storage device. In likemanner, if the other operating parameters indicate that the storagedevice is generally operating well within normal operating parameters,recording of information at low density to improve reliability may notbe required. Rather, the storage device operating with normal recordingdensity may provide adequate reliability for the specified purposes.

Thus, if the current capacity ratio and operating parameters indicatethat the number of low recording density zones should be reduced,element 3504 is next operable to re-record or migrate frames or blockspresently stored in a low recording density zone into a normal recordingdensity zone. As the data is migrated or re-recorded, mapping tableentries are updated appropriately to indicate that the physical datablocks corresponding to some logical addresses have been moved and toindicate a new recording density for the associated data. When all datain a particular low recording density zone has been migrated—leaving thezone emptied—the zone may be reconfigured as a normal recording densityzone for further storage of data. Reconfiguring the emptied zone fornormal density recording recovers physical storage capacity as comparedto the loss of capacity due to lower density recording. Processing ofthe method then continues looping back to element 3500 to continuebackground processing to monitor and reconfigure zones of the storagedevice.

If element 3502 determines that there is not a need to reduce the numberof low recording density zones, element 3506 is next operable todetermine whether the monitored operating parameter values indicate thatthe number of low recording density zones should be increased. Where theoperating parameters and the current capacity ratio indicate thatreliability may be enhanced by providing for more low density recordingand indicate that the current capacity ratio allows for such a reductionin usable physical capacity, element 3508 is operable to so increase thenumber of low recording density zone. Similar to the processing ofelement 3504, element 3508 migrates data currently recorded in a normalrecording density zone into one or more low recording density zones. Asdata is migrated, mapping table entries are updated to reflect the moveof some logical block addresses to different physical blocks at adifferent recording density. When all data in a particular normalrecording density zone has been migrated—leaving the zone emptied—thezone may be reconfigured as a low recording density zone for furtherstorage of data. Reconfiguring the emptied zone for low densityrecording reduces physical storage capacity. Hence the current capacityratio may be increased. Processing of the method then continues loopingback to element 3500 to continue background processing to monitor andreconfigure zones of the storage device.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 34 through 35 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to provide dynamic recording densities in dynamically mappedstorage device. Numerous equivalent methods and techniques will bereadily apparent to those of ordinary skill in the art to implement suchfeatures as a matter of design choice.

Field Flawscan

In typical present day disk drives, the manufacturer performs a flawscanat time of manufacture to identify flaws on the recordable mediasurfaces of the drive. To assure that the manufactured disk drive hassufficient usable storage media space for its specified capacity themanufacturer tests the disk drive by writing and reading back everyphysical location on the recordable media surfaces. This process,typically referred to as a “flawscan”, can be very time consuming ofteninvolving hours of test time for each disk drive.

Since all user data written to the dynamically mapped storage device isdynamically mapped from the user supplied logical address space (logicalblock addresses or LBAs) to the physical disk block address space (diskblock addresses or DBAs—blocks of variable, independent size relative tothe LBA size), features and aspects hereof permit reducing the portionof the storage device that need be scanned for flaws at time ofmanufacture. Complete flawscan processing is deferred to the fieldapplication of the storage device such that it may be completed afterthe storage device is used in an end user application—e.g., completedduring idle time of the storage device after it is first placed inservice.

In general, a minimal portion of the recordable surface area of thestorage device is fully scanned at time of manufacture. The minimalinitial flawscan at time of manufacture may include random scans ofportions of the recordable surfaces to assess the statistical likelihoodthat the drive will meet at least the specified total capacity. Inaddition, the manufacture time initial flawscan may include a smallportion of the total capacity sufficient to store data that a systemintegrator customer may use immediately upon installation of the storagedevice. For example, manufacturers of personal computers andworkstations often purchase large quantities of storage devices forintegration in their manufactured computing systems. The integratorimmediately installs an operating system and a standard compliment ofapplication programs on the storage devices as an aspect of theintegration process. Sufficient space to store such information may becertified by manufacture time flawscan operations. Thus sufficientinitial space may be certified by an initial flawscan to assure desiredresponsiveness to a system integrator's mass installation procedures. Ingeneral, the combination of the random sampling flawscan and the initialspace requirements flawscan (if any) at time of manufacture will stillrepresent a small fraction of the total storage capacity of the storagedevice—e.g., a few percent of the specified total physical capacity ofthe storage device.

FIG. 36 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide management of fieldflawscan in accordance with features and aspects hereof As noted above,disk controller 106 may include indirect logical to physical mappingelement 108 generally responsible for dynamic mapping features of thestorage device. An aspect of the logical to physical mapping element 108as noted above may include a field flawscan control element 3600operable to provide field flawscan to perform final flawscan (e.g.,completion of any initial flawscan performed prior to installation ofthe storage device in its intended application). Field flawscan controlelement 3600 may include various elements to aid in the flawscanprocessing in conjunction with substantially concurrent processing ofwrite requests by write request processing element 3602. Currentcertified capacity element 3604 represents any storage element used toindicate the amount of certified capacity presently available for writeoperations. Storage locations are “certified” by flawscan testing thatverifies proper storage and retrieval of information in each location ofthe storage device. As that certified capacity is used (e.g., byprocessing of write requests in element 3602), the current capacityindicator in element 3604 may be decreased. As final flawscan continuesby operation of element 3600, additional certified capacity may be addedto the indicator of element 3604. Further, as discussed in additionaldetail below, when supplied data of a write request is written touncertified storage capacity, it may be written with one or moreduplicate copies to help assure integrity of the recorded informationuntil the storage device is further certified. Duplicate migratoryelement 3608 may therefore be operable to move supplied data written touncertified locations of the storage device to certified locations asthe flawscan continues.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 3600 through 3608 shown as operable withinthe indirect logical to physical mapping element 108 of disk controller106 may be combined into fewer discrete elements or may be broken upinto a larger number of discrete functional elements as a matter ofdesign choice. Thus, the particular functional decomposition suggestedby FIG. 36 is intended merely as exemplary of one possible functionaldecomposition of elements within controller 106.

FIGS. 37 through 39 are flowcharts representing exemplary methodsoperable within a storage device controller (e.g., disk controller) inconjunction with the mapping features and aspects discussed hereinabove. In particular, FIG. 37 broadly represents a method operablewithin the storage device controller in accordance with features andaspects hereof to provide final or completed flawscan in fieldoperations (e.g., following installation of the storage device in itsintended initial application as distinct from time of manufacture orrelated manufacturing testing). Element 3700 of FIG. 37 represents theinitial flawscan that may be performed by a manufacturer of the storagedevice (e.g., at time of manufacture or related manufacture testing). Asnoted above, this initial flawscan may include a minimal portion of thetotal physical capacity of the storage device. An initial flawscan mayinvolve a sufficient capacity to permit initial installation of astandard operating system and applications as may be performed by asystem integrator or other end user of a newly purchased storage device.In addition, or in the alternative, the initial flawscan of element 3700may perform a statistical sampling of portions of the total physicalcapacity to validate or certify a small fraction of the total physicalcapacity while still providing a high probability of assurance that thespecified physical capacity of the storage device will be fullyavailable to the end user. Such statistical sampling techniques are wellknown in the industry and may entail statistical selection of randomlocations on the storage device (e.g., multiple radial locations on eachof multiple surfaces of the recording media of the storage device suchas a disk drive).

Following such initial flawscan performed by the manufacturer of thestorage device, the storage device may be packaged, sold, and shippedfor utilization by an end user in its intended initial application.Element 3702 represents processing by such an end user to install thestorage device in a related system and, optionally, to install theinitial host supplied data for use in the intended application (e.g.,operating system and/or initial applications with associated data as maybe performed by typical system integrators). Processing of element 3702may represent both manual processing to physically install a storagedevice as well as manual and/or automated procedures to initiallyinstall host supplied data for use in the intended initial application.

Elements 3704 through 3708 then represent processing within the storagedevice in accordance with features and aspects hereof to continue orcomplete the flawscan substantially in parallel with processing of writerequests to store host supplied data on the storage device. Element 3704is then operable to determine whether the final flawscan has alreadybeen completed. For example, each time the storage device is reset orpowered on, element 3704 will determine if the final flawscan to beperformed by the storage device has already been completed. If so,processing continues with element 3708 to simply continue normalprocessing of I/O requests including in particular write requests tostore data. If element 3704 determines that the final flawscan of thestorage device has not yet completed, elements 3706 and 3708 areoperable substantially concurrently within the storage device. As above,element 3708 processes write requests while element 3706 is operable tocontinue the final flawscan procedure until flawscan has beencompleted—thus certifying usability of each storage location of thestorage device. The two elements 3706 and 3708 are operablesubstantially in parallel. Thus, time consuming flawscan of the fullcapacity of the storage device is deferred until field installation ofthe storage device and may then be completed substantially in parallelwith ongoing utilization of the disk drive storage device for processingof write requests and other standard operations.

As discussed further herein below, element 3706 operable to perform thefinal flawscan of the storage device may be operable during idle periodsof the storage device. As used herein, “idle” periods are those periodsof time during which the storage device is not presently busy processingwrite requests or other host supplied requests. Therefore, the method ofFIG. 37 is essentially operable to complete flawscan with minimal or noperformance impact on the end user's utilization of the storage devicewhile dramatically reducing the time and associated cost and complexityassociated with manufacture testing to complete flawscan of the storagedevice.

Those of ordinary skill in the art will readily recognize that a flag orother indicia indicative of completion of the final flawscan may bestored within an appropriate nonvolatile memory associated with thestorage device including, for example, a reserved area of the recordablestorage media per se of the storage device.

Further, those of ordinary skill in the art will recognize that theinitial flawscan described by element 3700 may perform as much or aslittle flawscan processing as may be desired for the particular storagedevice application and architecture. In particular, the initial flawscanperformed at time of manufacture or in associated manufacture testingprocedures may be reduced to zero—in other words no initialcertification of flawless storage capacity. A manufacturer may choose tomarket such storage devices with a lower guaranteed storage capacity orhave a lower price point in view of the slightly higher probability ofreduced physical capacity due to manufacture flaws in the storage devicerecordable media.

FIG. 38 is a flowchart providing exemplary additional details of theprocessing of element 3706 of FIG. 37. As noted above, element 3706 isgenerally operable to continue the final flawscan procedures,substantially concurrently with ongoing write request processing, untilthe flawscan procedures have completed to thereby certify all locationsof the storage device. Element 3800 of FIG. 38 is first operable todetermine whether a write request is presently in process within thestorage device controller or is pending and awaiting processing byelements within the storage device controller storage device controller.If so, processing continues looping on element 3800 until such time asno write request processing is either in process or pending. As notedabove, “idle” periods of the storage device controller may be defined asperiods in which no write request is being processed or is pending or,more broadly, periods during which no host requested operations arecurrently in process or pending. When element 3800 determines that suchan idle period has been encountered, element 3802 is next operable toperform some additional quantum of flawscan processing to continuecertifying storage locations on the storage device that are at presentuncertified. As noted above, a storage element within the storage devicecontroller may store such progress information of the flawscanprocessing in a nonvolatile memory component so as to track progress inthe certification process of the final flawscan procedure within storagedevice. The particular quantum of processing to be performed by element3802 may be determined as a matter of design choice in accordance withthe needs of a particular application of features and aspects hereof.Element 3804 is next operable after completion of a quantum ofprocessing for the final flawscan to determine whether the finalflawscan processing has fully completed. If not, processing continueslooping back to element 3800 to await the next idle period such thatfurther quanta of flawscan processing may proceed by operation ofelement 3802. As each quantum of flawscan processing complete, storedindicia of the progress may be updated. If element 3804 determines thatfinal flawscan processing has completed, the processing of element 3706is complete and the appropriate nonvolatile storage information may beupdated to indicate the completion of the final flawscan processing.

FIG. 39 is a flowchart describing exemplary additional details of theprocessing of element 3708 of FIG. 37. As generally noted above, element3708 of FIG. 37 is operable to process host generated write requests tostore supplied data on the recordable media of the storage device. Theprocessing of element 3708 is substantially concurrent with processingof the final flawscan procedure until the flawscan processing hascompleted. Element 3900 of FIG. 39 is first operable to await receipt ofa next write request generated by an attached host system. Upon receiptof such a request, element 3902 is next operable to determine whetherthe final flawscan procedure has already completed. If so, element 3906is next operable to sense a pending write request from an attached hostsystem in accordance with normal write request processing proceduresassociated with the dynamically mapped storage device and as discussedherein above. Processing continues looping back to element 3900 to awaitreceipt of the next write request from an attached host system.

If element 3902 determines that the final flawscan processing has notyet completed, element 3904 is next operable to determine whethersufficient certified locations are available for writing the supplieddata in the current write band of the storage device. As noted above, inaccordance with the dynamic mapping features and aspects hereof, data ispreferably aggregated into frame meta structures and then written to therecordable media of the storage device in a particular current writeband. As noted above, a write band is a grouping of consecutive,adjacent radial track positions bounded on either side by a so calledguard band. The current write band represents available physicallocations for writing of host supplied data in response to receivedwrite requests. In general, the flawscan processing discussed above withrespect to FIGS. 37 through 38 attempts to stay physically just ahead ofthe write band as the storage device controller writes host suppliedinformation into the presently certified locations of the current writeband. In other words, flawscan certification attempts to keep up withthe sequential extension of the write band through physical locations ofthe current write band. If sufficient certified locations are availablein the current write band, processing continues with element 3906 asdiscussed above to complete the write request in accordance withstandard dynamically mapped storage procedures of the dynamically mappedstorage device. Processing continues looping back to element 3900 toawait receipt of a next host write request.

If element 3904 determines that the current write band does not havesufficient certified locations, processing continues with element 3908to locate sufficient physical locations in each of one or more alternatewrite bands certified by the final flawscan proceeding substantiallyconcurrently. This may require that the disk controller defragment therecordable media to make available sufficient space. Otherwise, the diskcontroller may wait for additional locations to be certified by thefinal flawscan process before continuing the writing process.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 37 through 39 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to provide field flawscan substantially concurrently with ongoingwrite request processing within a dynamically mapped storage device.Numerous equivalent methods and techniques will be readily apparent tothose of ordinary skill in the art to implement such features as amatter of design choice.

Appended Metadata

It is desirable to analyze or diagnose operation of a storage device toanticipate failures or to analyze performance problems or potentialperformance improvements. Appended metadata may be stored in thedynamically mapped disk drive indicating historical and currentoperation of the dynamically mapped storage device in its end useapplication. The appended metadata may be used in the dynamically mappedstorage device for purposes of analyzing or diagnosing the operation ofthe dynamically mapped storage device.

Since all user data written to the dynamically mapped storage device isdynamically mapped from the user supplied logical address space (logicalblock addresses or LBAs) to the physical disk block address space (diskblock addresses or DBAs—blocks of variable, independent size relative tothe LBA size), features and aspects hereof-permit utilizing a portion ofphysical storage capacity for storing metadata relating to historicaland current operation of the storage device in its end use applicationenvironment. While the logical to physical storage capacity ratio(current capacity ratio as discussed above) remains relatively low,physical storage capacity may be used to store metadata associated withcurrent and past operation of the storage device to thereby enablediagnostic and analytical processing to alter or tune future operationof the storage devices and/or to diagnose or resolve errors in thestorage device operation.

In general, while the current capacity ratio is relatively low (i.e.,under a predetermined threshold), metadata may be added (appended) tophysical disk blocks written (and/or each frame written). The metadatamay be useful to diagnose or analyze operation of the storage device. Asthe current capacity ratio increases (e.g., above a predeterminedthreshold), subsequent written data may eliminate the appended metadata.As the current capacity ratio continues to rise, data previouslyrecorded with appended metadata may be re-recorded (e.g., migrated) to anew, logically mapped physical storage location without the appendedmetadata to thereby free physical space for user data storage as needed.When so migrating data to be re-recorded, data may be selected based onany number of factors including, for example, its relative criticalityto the application's use of the storage device (as also discussedabove).

Exemplary metadata may include: track position information relating tothe recorded data, operating temperature at the time of recordation ofthe data, head assembly flying height at the time of the data recording,time of day of the data recording, etc. Track position information maybe determined (from servo information) just prior to the datarecordation or as the data is being recorded and then appended to theend of the data as it is written. Such information may be used todetermine the quality of servo track following features of the storagedevice and hence the quality of the data so recorded on the storagedevice. Temperature information may include current temperature of theread/write head assembly (e.g., the assembly pre-amplifier) just priorto or during writing of the data and then appended to the end of thewritten data. Further, the temperature information may include othertemperatures sensed from within the storage device such as from sensorson the controller printed circuit board or elsewhere associated with thestorage device. Similarly, read/write head assembly flying height may bedetermined just prior to or during writing of the data and may beappended to the written data. Current time of day may also be capturedjust prior to or as the data is written and appended to the writtendata.

The time of day may be useful in analyzing the change in operatingcharacteristics of the storage device over time. In addition, the timeof day, in conjunction with the “unwind” features discussed above, maybe used to restore the data stored on the storage device to an earlierrecorded version. As noted above, the various mapping table structuresdiscussed in detail above may be recorded in multiple physical locationsof the storage device recordable media. Further, the multiple copies ofthe mapping tables may represent different points in time as data isrecorded on the storage device. Still further, data written to thestorage device that overwrites the same logical block address ofpreviously recorded data need not erase the earlier copy. Rather, themapping features hereof allow the earlier copy to remain stored on thestorage device and the new data may be recorded at a new physicallocation. The mapping table structures may then map both physical copiesof the data to the same logical block address and may also record thetime of day associated with each copy. Time of day informationassociated with recorded data may therefore be used when “unwinding” thestorage device to an earlier state and in particular to unwind to aprecise earlier date and time.

FIG. 40 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to generate and utilize appendedmetadata in accordance with features and aspects hereof. As noted above,disk controller 106 may include indirect logical to physical mappingelement 108 generally responsible for dynamic mapping features of thestorage device. An aspect of the logical to physical mapping element 108as noted above may include a write request processor 402 that includesmetadata generation element 4000 for generating metadata associated withthe writing of host supplied data and for storing the generated metadatain conjunction with the stored host supplied data. As discussed above,mapping element 108 may also include features to determine a currentcapacity ratio 4004 indicating the volume of logical data stored on thestorage device relative to the actual physical locations utilized on thestorage device. As discussed further herein below, metadata generationelement 4000 is operable responsive to the current capacity ratio 4004such that the additional metadata may be gathered and appended to datawritten to the storage device in accordance with the current capacityratio as compared to one or more predetermined threshold levels. Forexample, when the current capacity ratio 4004 indicates that there issufficient room to do so, metadata generation element 4000 may beoperable responsive thereto to generate metadata and append the metadatato associated host supplied data stored in the storage device.Conversely, where the current capacity ratio 4004 indicates thatinsufficient physical space remains in the storage device relative tothe volume of logical data stored therein, metadata generation element4000 will refrain from appending metadata to host supplied data fromsubsequent write requests until such time (if ever) when the currentcapacity ratio again falls below a predetermined threshold value.

Metadata generation element 4000 may retrieve time of day informationfrom time of day element 4008 and may receive values of currentoperating parameters of the storage device from element 4010. Those ofordinary skill in the art will readily recognize common devices within astorage device that may provide such information useful for the metadatagenerator 4000. In particular, the time of day circuit 4008 may be anyof several well-known commercially available clock circuits that providetime of day information to devices coupled thereto. Still further, thoseof ordinary skill and the art will readily recognize numerous otheroperating parameters that may be provided to metadata generation element4000 by element 4010. For example, servo controls for track followingmay provide the ability to read the current track position to determinehow far off center track the read/write head assembly is as it fliesover a radial track position. Or, for example, various temperaturemonitoring elements may be provided within a storage device indicatingthe current temperature of the operating storage device. A temperatureof the read/write write head, per se, as well as other temperaturesensors within or otherwise associated with the storage device may beprovided. Or, for example, servo control mechanisms controlling headflying height may provide the ability for the metadata generator to readthe current flying height of the read/write head as it passes over therotating storage media.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 4000 through 4010 shown as operable withinthe indirect logical to physical mapping element 108 of controller 106may be combined into fewer discrete elements or may be broken up into alarger number of discrete functional elements as a matter of designchoice. Thus, the particular functional decomposition suggested by FIG.40 is intended merely as exemplary of one possible functionaldecomposition of elements within controller 106.

FIG. 41 is a flowchart describing an exemplary method in accordance withfeatures and aspects hereof to process a write request received from anattached host system. As noted above, as determined by the currentcapacity ratio, metadata may be gathered and appended to the hostsupplied data to be recorded on the storage media of the storage device.Element 4100 is therefore first operable to receive a write request froman attached host system with host supplied data. In response toreceiving such a write request, element 4102 is next operable todetermine whether the value of the current capacity ratio is above orbelow a predetermined threshold value. If element 4102 determines thatthe current capacity ratio is not below the predetermined thresholdvalue (e.g., insufficient space may be available for further appendingof metadata), element 4110 is operable to complete the write request byrecording the host supplied data without any appended metadata inselected physical locations of the storage device. In addition, and inaccordance with standard write request processing for the dynamicallymapped storage device, the recorded data is mapped through the mappingtable structures described above so that the logical block addressprovided by the host system is mapped to the next available selectedphysical locations in which the host supplied data is written.

If element 4102 determines that the current capacity ratio is below thepredetermined threshold value, element 4104 is next operable to gathermetadata to be appended to the host supplied data for recording on thestorage device recordable media. As noted above, the metadata mayinclude, for example, current flying height of the read/write headassembly, current on/off track location information from the trackfollowing servo mechanism, time of day information, etc. Element 4106 isthen operable to record the host supplied data along with the gatheredmetadata in the next available selected physical locations and to mapthe supplied logical block addresses to the selected physical locationsin which the host supplied data and the metadata is recorded. As notedabove, element 4104 is operable to gather the desired metadata inadvance of recording the supplied data with the appended metadata or thegathering of metadata and recording of host supplied data may besubstantially overlapped such that the metadata is gatheredsubstantially concurrently with the time of recording some portion ofthe host supplied data. Thus, those of ordinary skill in the art willreadily recognize that elements 4104 and 4106, in particular, may bemerged logically into a single operation whereby as host supplied datais recorded the associated metadata is gathered and written at the endof recordation of the host supplied data. Such design choices will bereadily apparent to those of ordinary skill in the art.

FIG. 42 is a flowchart describing an exemplary method operable withinthe dynamically mapped storage device to monitor the current capacitythreshold value and, when appropriate, to migrate previously recordeddata with appended metadata to new locations re-recording the hostsupplied data devoid of appended metadata. Thus the method of FIG. 42 isgenerally operable as a background task within the storage devicecontroller to reduce the current capacity ratio as the volume of stored,host supplied data increases. Thus, elements 4200 through 4204 aregenerally continuously operable as background processing within thestorage device controller of the dynamically mapped storage device.

Element 4200 is operable to loop until the current capacity ratioreaches the predetermined threshold value. When the current capacityratio is detected as having exceeded met or exceeded the predeterminedthreshold value, element 4202 is next operable to locate previouslyrecorded data having appended metadata associated therewith. Element4204 is then operable to migrate the data located by operation ofelement 4202 into new physical locations such that the host supplieddata is re-recorded devoid of the previously appended metadata. Thepreviously recorded copy of the re-recorded data with its appendedmetadata may then be freed for subsequent use in processing additionalwrite requests. Dynamically mapping structures discussed above areappropriately adjusted to map the host supplied logical block address ofthe earlier previously recorded data to the newly selected physicallocation.

Those of ordinary skill in the art will readily recognized thatprocessing of element 4202 may be in accordance with any desiredselection criteria as a matter of design choice. For example, frequencyof access to the data, criticality of the data, and other selectioncriteria algorithms may be processed by element 4202 to determine whichpreviously recorded data should be migrated in such a manner as torelinquish physical storage capacity previously used for storingmetadata. For example, as noted above, particularly critical, frequentlyaccessed data may most beneficially utilize the recorded metadata. Or,for example, previously recorded data with appended metadata may beselected for migration such that remaining appended metadata (if any)provides a desirable statistical sampling of portions of the recordablemedia of the storage device and/or a statistical sampling of metadatagathered at a variety of times during operation of the storage device.Thus, appended metadata analysis may most beneficially apply statisticalsampling techniques for analyzing current operation of the storagedevice.

FIG. 43 is a flowchart describing another exemplary method similar tothat of FIG. 41 discussed above for processing of received writerequests with host supplied data. In particular, the method of FIG. 43specifically calls for recordation of at least the time of day asmetadata appended to recorded host supplied data. Time of dayinformation coupled with the multiple logically mapped indirections ofhost supplied data and the various mapping tables may be used to“unwind” the data stored on the map storage device to an earlier dateand time. As discussed above, a logical block address mapped by themapping tables may provide for multiple mappings. For example, multiplecopies may be recorded to improve reliability through redundancy. Or,for example, in accordance with the ability to unwind the content of thestorage device, earlier host supplied data recorded at a physicallocation and mapped to a logical block address may be retained when newdata is supplied by the host at the same logical block address. Throughuse of the mapping tables, the more recently written version may bemapped to the supplied logical address but the earlier recordedinformation may also be mapped through the mapping table structures. Inaddition, as discussed above, multiple earlier versions of the mappingtable structures may be saved in reserved physical locations of thestorage device. In other words, by local processing within thedynamically mapped storage device utilizing appended metadata includingtime of day and other data duplication/mapping techniques discussedabove, a disk drive storage device, per se, may permit unwindrestoration of its contents to an earlier time of day for backup orarchival recovery purposes.

The method of FIG. 43 suggests the particular utilization of time of dayinformation both incorporated and appended as metadata and, as required,recorded within the mapping table structures to enable tracking of thetime of overwriting of logical block addresses within the dynamicallymapped storage device. Element 4300 is first operable to receive a writerequest from an attached host system providing host supplied data andlogical block addresses for recording the supplied data. Element 4302then determines whether the current capacity ratio is above or below apredetermined threshold value. If the current capacity ratio is at orabove the predetermined threshold value, element 4310 is operable torecord the host supplied data devoid of appended metadata in the nextavailable selected physical locations. Mapping table structuresdiscussed above are also updated to map the host supplied logical blockaddresses to the selected, next available physical locations.

As the physical storage capacity is used up in the storage device,metadata including time of day may not be recorded, hence the recordedhost supplied data may fail to provide accurate time of day information.However, mapping table structures mapping the newly recorded data to thehost supplied logical block addresses may include desired timinginformation to note the time of recordation. Thus, time of dayinformation may be recorded in the mapping table structures when thecurrent capacity ratio indicates the need to reduce the volume ofappended metadata.

If element 4302 determines that the current capacity ratio is stillbelow the predetermined threshold value, element 4304 is operable togather current metadata information including at least the current timeof day information. Element 4306 is then operable to record the hostsupplied data and gathered metadata (including at least time of dayinformation) in selected, next available, physical locations of thestorage device. Further, mapping table structures associated herewithare updated by processing of element 4306 to reflect the new physicallocation of the hosts supplied logical block addresses. The metadatagathered by element 4304 is appended to the recorded host supplied data.As above with respect to FIG. 41, elements 4304 and 4306 may be operablesubstantially concurrently such that the acquisition and gathering ofmetadata including at least current time of day overlaps withrecordation of a portion of the host supplied data. Also as above withrespect to FIG. 41, mapping tables associated with the logical mappingstructures discussed above may also include time of day information as atechnique for identifying the current time of recordation of associatedhost supplied data.

Older data previously recorded at the same logical block address may beremoved if the current capacity ratio suggests the need to recoverphysical storage space. Alternatively, older data previously recordedmay remain stored and mapped to the same logical block address in themapping tables. The methods used to locate a host specified logicalblock address for reading may then locate the most recent copy ofrecorded data as indicated by the recorded time of day metadata (or asindicated by the time of day recorded in the mapping table structures).By so retaining older, previously recorded copies of physical datablocks corresponding to a host supplied logical block address, theearlier recorded content of the storage device may be controllablyrestored by operation of the storage device.

FIG. 44 is a flowchart describing an exemplary method operable in thestorage device controller of a logically map storage device—to performand “unwind” operation in response to an appropriate request. Such arequest may be provided by a diagnostic tool through a diagnosticinterface of the storage device and/or may be provided by a specialcommand received from an attached host system. As a matter of designchoice, those of ordinary skill in the art will readily recognize avariety of security and authorization features to help assure that onlyappropriately authorized users and/or applications may invoke such arequest.

Element 4400 therefore represents processing to receive an appropriatelyauthorized request to unwind the contents of the dynamically mappedstorage device to a previous, specified time of day. Element 4402 isthen operable to analyze the recorded information on the storage deviceto determine whether the requested unwinding to the specified time ofday is achievable. As noted above, responsive to changes in the currentcapacity ratio, data may be recorded with or without appended metadatainclusive of time of day information. Still further, as noted above,logical mapping table structures may optionally include time of dayinformation useful wherein the appended metadata is not available forparticular recorded data. Therefore processing of element 4402determines whether all requisite mapping tables and/or metadatainformation is available to identify all changes to the content of thedynamically mapped storage device that followed the specified time ofday. If all required information is not available to accomplish therequested unwind procedure, element 4410 is operable to return anappropriate failure status code to the requesting user or program.

If all required information is available to unwind the content of thedynamically mapped storage device to the specified earlier time, element4404 is next operable to appropriately re-organize the mapping tablessuch that only data written to the storage device that predates thespecified time may be accessed by subsequent read host requests. Element4406 may optionally remove all the stored data that post-dates thespecified earlier time so as to recover additional physical space usefulfor storing other host supplied information and appended metadata.Element 4406 is optional in that later, post-dated information may beretained and the mapping tables may simply be reorganized to use theearlier stored version of all stored data. Elements of 4404 and 4406therefore perform the desired unwind operation back to a specified timeby restoring mapping tables to the earlier specified time and byremapping logical block addresses to corresponding physical blockspreviously recorded. Lastly, element 4408 returns a successful statusindication to the requesting program or user indicating that the unwindoperation was successfully completed and that the logical content of thedynamically mapped storage device has thus been restored to thespecified earlier date and time.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 41 through 44 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to provide appended metadata in a dynamically mapped storage.Numerous equivalent methods and techniques will be readily apparent tothose of ordinary skill in the art to implement such features as amatter of design choice.

Write Fault Recovery

As a disk drive writes data to a track of the recordable media, writefault errors may occur in instances where data is not correctly writtento disk, such as when the write head deviates too far from the trackcenter. If the data is written too far from the center of the track, itmay be unreadable during subsequent read processes. In some cases wherethe write head deviates too far from the track center data on adjacenttracks written earlier in time may be overwritten and destroyed. Aspresently practiced, such errors may not be recoverable, and the dataoverwritten may be destroyed. Additionally, recovery from these errorsimposes large penalties on the disk drive.

In accordance with features and aspects hereof, all user data written tothe dynamically mapped storage device is dynamically mapped from theuser supplied logical address space (logical block addresses or LBAs) tothe physical disk block address space (disk block addresses orDBAs—blocks of variable, independent size relative to the LBA size).Thus features and aspects hereof permit recovery from write faulterrors, such as off-track position errors, without significantperformance losses while allowing for the recovery of over-written data.An off-track position error occurs when the write head deviates too farfrom the center of the track, in which the written data may beunreadable. Further, an off-track position error may encroach previouslywritten adjacent tracks, destroying data contained in the adjacenttracks.

FIG. 45 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide handling of anoff-track position error encountered while writing user supplied data toa recordable media. As noted above, disk controller 106 may includeindirect logical to physical mapping element 108 generally responsiblefor dynamic mapping features of the storage device. An aspect of thelogical to physical mapping element 108 as noted above may include writerequest processing element 4500 operable to process requests to writedata to the recordable media. Write request processing element 4500 mayinclude write fault detection and correction element 4502 operable todetect and correct write fault errors occurring during the writingprocess. Disk controller 106 may include track following servo controland sense element 4504 operable to detect and control the position ofthe write head. Servo controls for track following may provide theability to read the current track position to determine how far offcenter track the write head assembly is as it flies over a radial trackposition. Position error detection element 4508 is operable generally todetect position errors of the write head, for example in response to aposition error signal (PES) from track following servo control and senseelement 4504.

Write fault detection and correction element 4502 may include positionerror threshold values 4510, representing threshold values for detectingan off-track position error. There may be multiple position errorthreshold values 4510. For instance, a first threshold value mayindicate an off-track position error in a direction in which noencroachment of an adjacent track may occur. A second threshold valuemay indicate an off-track position error in a direction in whichencroachment of data in an adjacent track may occur. A third thresholdvalue for instance may indicate that encroachment of data in an adjacenttrack has occurred. Thus, write fault detection and correction element4502 may determine whether to re-write the incorrectly written logicalblock as well as a logical block that may have been encroached uponduring the off-track position error. Write fault detection andcorrection element 4502 may include re-write/re-map processor 4506operable to re-write and re-map data that was incorrectly written to therecordable media, as well as data overwritten by an off-track positionerror.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 4500 through 4510 shown as operable withinthe indirect logical to physical mapping element 108 of disk controller106 may be combined into fewer discrete elements or may be broken upinto a larger number of discrete functional elements as a matter ofdesign choice. Thus, the particular functional decomposition suggestedby FIG. 45 is intended merely as exemplary of one possible functionaldecomposition of elements within disk controller 106.

FIG. 48 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller 106 of FIG. 45) inconjunction with the mapping features and aspects discussed herein abovefor handling off-track position errors. In particular, FIG. 48 broadlyrepresents a method operable within disk controller 106 in accordancewith features and aspects hereof to provide recovery from a write faulterror. In steady state operation of a dynamically mapped storage device,a buffer stores the most recently written blocks of information (writtento sequential physical locations regardless of host supplied logicaladdress). The buffer is managed in a circular fashion discussed abovesuch that new data to be written is added to the buffer in space vacatedby older written, information.

When the disk drive is first powered on or reset, a buffer is filledwith recently written physical blocks (e.g., the most recently writtentracks). The recently written physical blocks are used to recover froman off-track position error or any other type of write error. Element4802 represents disk controller 106 reading the recently writtenphysical blocks into the buffer. Element 4804 represents disk controller106 commencing normal operation. The disk drive may continue to store ina buffer the recently written physical blocks. As the disk drivecontinues normal operations and writes logical blocks supplied by anattached host, the contents of the buffer may change to reflect therecently written physical blocks written to the recordable media afterexecution of element 4802. Thus, subsequently written physical blocksmay be added to the buffer, and the oldest previously written physicalblocks in the buffer may be dropped or replaced from the buffer as newdata is added. For instance, the buffer may be a circular buffer, andnewly written physical blocks replace the most previously writtenphysical blocks. Those of ordinary skill in the art will recognize thatthe size of the buffer may be selected depending on various designcriteria. For instance, the buffer may store several tracks of recentlywritten data to recover from an off-track position error that encroachesdata on another track several tracks away.

Once normal operations of the disk drive commence, the disk drive mayreceive a write request from an attached host. Element 4810 representsdisk controller 106 receiving a supplied logical block to be written toa recordable media. The supplied logical block may be provided by anattached host, or may be provided by disk controller 106 for internaluse by the disk drive. Element 4812 represents disk controller 106beginning to write the supplied logical block at a first physical blockaddress of the recordable media.

In 4814, disk controller 106 determines whether the write is complete(e.g., whether all blocks buffered to be written have been successfullywritten). If the writing process is complete, then the write request isfinished. If the write is not complete, then disk controller 106determines whether an off-track position error has occurred in element4816. The off-track position error for example may be signaled by aposition error signal (PES). If no position error has occurred, then thewrite request is completed.

If an off-track position error has occurred while writing a block, thenthe incorrectly written logical block may be rewritten later at a secondphysical block address of the recordable media. Element 4818 representsdisk controller 106 re-writing the supplied logical block at the secondphysical block address. Element 4820 represents disk controller 106adjusting a mapping table to map the supplied logical block at thesecond physical block address. After the mapping table is adjusted, thewrite request is finished.

FIG. 49 is a flowchart providing exemplary additional details of theprocessing of element 4818 of FIG. 48. As noted above, element 4818 isgenerally operable to re-write supplied logical blocks at a secondphysical block address of the recordable media. Element 4902 representsdisk controller 106 appending the supplied logical block to a buffer tobe written to the recordable media. Element 4904 represents diskcontroller 106 writing the buffer to the recordable media in the orderin which the data is stored in the buffer. Thus, the supplied logicalblock is re-written at the second physical block address responsive toreaching a position in the buffer of the supplied logical block. Thebuffer will be described in additional detail below.

FIG. 50 is a flowchart providing exemplary additional details of theprocessing of element 4816 of FIG. 48. As noted above, element 4816 isgenerally operable to re-write a supplied logical block at a secondphysical block address of the recordable media. In particular, FIG. 50broadly represents a method operable within the storage controller inaccordance with features and aspects hereof to provide recovery of apreviously written physical block encroached during a write fault error.As described with respect to FIG. 48, an off-track position error mayencroach a previously written physical block. In addition to re-writingthe incorrectly written physical block, disk controller 106 may need tore-write the encroached previously written physical block. Element 5002represents disk controller 106 determining whether a previously writtenphysical block has been encroached during the off-track position error.If no encroachment has occurred, then processing may continue at element4818.

If the previously written physical block has been encroached during theoff-track position error, then disk controller 106 retrieves thepreviously written physical block from the buffer in element 5004. Asdiscussed above, disk controller 106 stores tracks of previously writtenphysical blocks in a buffer to allow recovery from an off-track positionerror.

Element 5006 represents disk controller 106 re-writing the previouslywritten physical block at a new physical block address of the recordablemedia. The previously written physical block is associated with alogical block address in the mapping table. Element 5006 represents diskcontroller 106 adjusting the mapping table to map the logical blockaddress to the new physical block address. Thus, rather than stoppingthe writing process to re-write the encroached previously writtenphysical block, disk controller 106 may re-write the encroached logicalblock in the sequence of supplied logical blocks currently being writtento the recordable media.

An off-track position error may occur in two directions, in onedirection no data may be encroached, and in another direction data maybe encroached. FIG. 46 illustrates an off-track position error in adirection in which no encroachment of an adjacent track may occur. Asequence of logical blocks numbered 1-10 are previously written on trackN−1. Further, logical blocks 11-17 are buffered to be written on trackN. As the blocks are written, an off track (PES) error may occur. Thewrite head is shown presently writing data to track N. Threshold 1represents a position of the write head in a direction in whichencroachment of an adjacent track (Track N−1) may occur. Threshold 2represents a position of the write head in a direction in which noencroachment of an adjacent track may occur (Track N+1). As the diskdrive writes Track N, the write head deviates from the track center ofTrack N in the direction of Track N+1, a presently unwritten track. Oncea supplied logical block is written by the write head past threshold 2(e.g., supplied logical block 16*), an off-track position error occurs,and the supplied logical block may need to be re-written. Suppliedlogical block 16 may be re-written at a second physical block address(e.g., supplied logical block 16′). For example, the write headcontinues writing a sequence of supplied logical blocks, and re-writesthe incorrectly written supplied logical block at the end of sequence.Thus, the writing process is not aborted, and writing continues withouta performance loss of one or more revolutions of the disk drive.Alternatively, the write head may re-write the incorrectly writtenlogical block prior to continuing writing the sequence of suppliedlogical blocks to maintain a logical order of the blocks.

FIG. 47 is similar to FIG. 46 showing writing of logical blocks 1-10 ontrack N−1 and blocks 11-17 on track N. The off track position error isin a direction in which encroachment of an adjacent track occurs. As thedisk drive writes Track N, the write head is shown deviating from thetrack center of Track N in the direction of Track N−1, a previouslywritten track. An off-track position error occurs, and supplied logicalblocks 15 and 16 are incorrectly written past Threshold 1, encroachingTrack N−1. Further, supplied logical block 16 encroaches onto suppliedlogical block 6. Thus, logical blocks 6, 15 and 16 may be rewrittenfollowing the completion of writing the sequence of supplied logicalblocks to the recordable media. Since the disk drive stores recentlywritten physical blocks in a buffer, logical block 6 may be recoveredfrom the buffer, and be re-written in Track N (e.g., logical block 6′).Logical blocks 15 and 16 may be re-written as illustrated by logicalblocks 15′ and 16′. Thus, the disk drive recovers from the write faultwithout aborting the writing process, and the encroached physical blockis recovered and rewritten at a second physical block address.Performance losses associated with moving the write head back to thelocation of the encroached physical block are eliminated.

As can be seen in FIGS. 46-47, recovery from such off-track write errorsuses previously written information from an adjacent encroached track.Such previously written data and new data to be written may be stored ina buffer (referred to above in FIG. 9 as a “write band”). FIGS. 55-58are block diagrams depicting an exemplary buffer used by a disk drive.Buffer 5500 as illustrated is a circular buffer storing recentpreviously written physical blocks 5506, as well as physical blocksawaiting writing 5510. Those of ordinary skill in the art will recognizethat buffer 5500 may be of any type of equivalent data structure capableof storing recent previously written physical blocks 5506 as well asphysical blocks awaiting writing 5510. As is generally known if the art,data for a write request may simply be queued for later posting with therequested write data stored in the cache memory (e.g., buffer 5500) orotherwise managed within disk controller 106. Such techniques are oftenreferred to as write-back caching in that the request is completed withrespect to the host as soon as the disk controller has the requeststored in its local cache memory. The data is then later posted orflushed to the persistent recordable media under control of the diskcontroller. FIGS. 56-58 illustrate the contents of buffer 5500 asoperations modify buffer 5500.

When moving through buffer 5500 during the writing process, diskcontroller 106 moves forward one step each time data is written, andwhen disk controller 106 passes the end of buffer 5500, then diskcontroller 106 starts again at the beginning. The size of circularbuffer 5500 may be selected to store several tracks of previouslywritten data, as well as to provide adequate capacity to accommodatepending write requests received from an attached host. As discussedabove, the size of a write band 900 is a function for example of thewrite cache size (e.g., buffer 5500) of disk controller 106. The currentwrite band represents available physical locations for writing of hostsupplied data in response to received write requests. Thus, the size ofbuffer 5500 may be selected to correspond to write band 900 used by thedynamically mapped storage device, or may be a smaller portion of the“write band” size such as a few tracks of stored data.

As discussed above, the previously written physical blocks stored inbuffer 5500 are used to recover from an off-track position errorencroaching on previously written data. When the disk drive first powerson, several tracks of previously written physical blocks may be read andstored in buffer 5500. Current position 5508 represents a suppliedlogical block presently being written or next to be written to therecordable media by the write head. Those of ordinary skill in the artwill recognize that a typical buffer used in a disk drive would belarger than illustrated in FIG. 5500, and buffer 5500 is shown witheight positions for simplicity of this discussion.

In FIG. 55, the current position 5508 of the buffer 5500 is at logicalblock 5, indicating that the write head is currently writing logicalblock 5 to the recordable media. Logical blocks 1-4 are previouslywritten 5506, (i.e. earlier on the current track and on one or moreearlier adjacent tracks) and logical blocks 6-8 are awaiting writing5510. Assume that an off-track position error occurs while writinglogical block 5. Logical block 5 may be appended to buffer 5500 byelement 4902 to be later rewritten at a new physical location.

FIG. 56 illustrates the contents of buffer 5500 after logical block 5 isappended to buffer 5500. The position of logical block 5 in buffer 5500is no longer between the position of logical blocks 4 and 6. Rather, theposition of logical block 5 has changed to the end of buffer 5500. Thecurrent position 5608 of buffer 5500 is now logical block 6, and logicalblocks 7-8 and 5 are awaiting writing 5610.

FIG. 57 illustrates the contents of buffer 5500 once the currentposition 5708 again reaches logical block 5 after logical blocks 6-8 arewritten to the recordable media. Thus, logical blocks 3-4 and 6-8 areshown as previously written 5706, and two more logical blocks 9 and 10have been added (appended) to the buffer 5500 following the new positionof logical block 5, and are awaiting writing 5710. Thus, logical block 5will follow logical block 8 on the recordable media.

Referring back to FIG. 55, assume that the current position 5508 islogical block 5, and further assume for example that while writinglogical block 5 in element 4812 that logical block 1 is encroachedduring the off-track position error and needs to be rewritten. FIG. 58illustrates the contents of buffer 5500 after disk controller 106appends logical blocks 1 and 5 to buffer 5500. Logical block 2 is notshown because it is deemed far enough away to not be encroached. Writtenblocks that fall out of a buffer do so because they are sufficiently faraway as to not be encroached by subsequent writes with off-trackposition errors. Logical blocks 3 and 4 are previously written 5806, andlogical blocks 7-8, 1 and 5 are awaiting writing 5810. The currentposition 5800 of buffer 5500 is presently logical block 6. Thus, logicalblocks 1 and 5 may be re-written on the recordable media followinglogical block 8. Those of ordinary skill in art will recognize thatlogical blocks 1 and 5 may be re-written in any order. Thus, logicalblock 1 may be re-written before logical block 5, or logical block 5 maybe re-written before logical block 1.

Those of ordinary skill in the art will recognize that an off-trackposition error would normally encroach a logical block at least onetrack length of data away from the current position 5508. Thus, thewriting of logical block 5 would not normally encroach a logical orphysical block four positions away. The length of distance betweencurrent position 5508 and logical block 1 is shown for the sake ofsimplicity of the discussion.

FIG. 51 is a flowchart providing exemplary additional details of theprocessing of element 5006 of FIG. 50. As noted above, element 5006 isgenerally operable to re-write the previously written physical block ata new physical block address of the recordable media. Since thepreviously written physical block is stored in a buffer includingpreviously written logical blocks as well as logical blocks to bewritten, disk controller 106 may change the position of the previouslywritten physical block in the buffer to follow logical blocks to bewritten to the recordable media.

Element 5102 represents disk controller 106 changing the position of thepreviously written physical block in buffer 5500. Element 5104represents disk controller 106 writing buffer 5500 to the recordablemedia in the order in which the data is stored in buffer 5500. Thus, thepreviously written physical block is re-written at the new physicalblock address responsive to reaching a position in buffer 5500 of thepreviously written physical block. For instance, assume that logicalblock 1 in FIG. 55 is encroached during the off-track position error andneeds to be re-written. Prior to the encroachment, logical block 1 ispreviously written 5506. The position of logical block 1 may be changedin buffer 5500, as illustrated in FIG. 58, so that logical block 1 isnow awaiting writing 5810.

FIG. 52 is a flowchart representing another exemplary method operablewithin a storage device controller (e.g., disk controller) inconjunction with the mapping features and aspects discussed herein abovefor handling off-track position errors. In particular, FIG. 52 broadlyrepresents a method operable within the storage controller in accordancewith features and aspects hereof to provide recovery from a write faulterror.

Element 5202 represents write request processing element 4500 receivinga supplied logical block to be written to a recordable media. Thesupplied logical block may be provided by an attached host, or may beprovided by disk controller 106 for internal use by the disk drive.

Element 5204 represents write request processing element 4500 adding thesupplied logical block to a buffer. For instance, the supplied logicalblock may be appended to buffer 5500 as illustrated by logical block 9awaiting writing 5710 in FIG. 57.

Element 5206 represents write request processing 4500 writing thesupplied logical block at a first physical block address of therecordable media. In 5208, position error detection element 4508determines whether an off-track position error has occurred. If noposition error has occurred, then the write request is completed.

If a position error has occurred, then write disk controller 106recovers from the off-track position error and re-writes the suppliedlogical block at a second physical block address.

FIG. 53 is a flowchart providing exemplary additional details of theprocessing of element 5210 of FIG. 52. As noted above, element 5210 isgenerally operable to recover from the off-track position error. Element5302 represents disk controller 106 changing a position of the suppliedlogical block in the buffer. Element 5102 represents disk controller 106changing the position of the previously written physical block in thebuffer. Element 5104 represents disk controller 106 writing the bufferto the recordable media in the order in which the data is stored in thebuffer. Thus, the previously written physical block is re-written at thenew physical block address responsive to reaching a position in thebuffer of the previously written physical block. For instance, assumethat logical block 1 in FIG. 55 is encroached and needs to bere-written. Prior to the encroachment, logical block 1 is previouslywritten 5506. The position of logical block 1 may be changed, asillustrated in FIG. 58, so that logical block 1 is now awaiting writing5810.

FIG. 54 is a flowchart providing exemplary additional details of anotherembodiment of the processing of element 5210 of FIG. 52. As noted above,element 5210 is generally operable to re-recover from the off-trackposition error. Element 5402 represents disk controller 106 sensing adirection of the off-track position error. Element 5404 represents diskcontroller 106 determining whether the off-track position error exceedsa first threshold. For instance, exceeding the first threshold mayindicate that data stored in the first physical block address (e.g., thesupplied logical block) is unreliable, and that the supplied logicalblock needs to be re-written. If the first threshold is not exceeded,then the write request is complete.

If the first threshold is exceeded, then in element 5406 disk controller106 re-writes the supplied logical block at the second physical blockaddress responsive to reaching a position in the buffer of the suppliedlogical block.

Element 5406 represents disk controller 106 determining whether theoff-track position error exceeds a second threshold. For instance,exceeding the second threshold may indicate that data stored in thepreviously written physical block is unreliable, and that the previouslywritten physical block needs to be re-written. If the second thresholdis not exceeded, then the write request is complete.

If the first threshold is exceeded, then in element 5410 disk controller106 changes a position in the buffer of the previously written physicalblock. Element 5412 represents disk controller 106 writing the buffer tothe recordable media in the order in which the data is stored in thebuffer. Thus, the previously written physical block is re-written at thenew physical block address responsive to reaching a position in thebuffer of the previously written physical block. Element 5412 representsdisk controller 106 adjusting the mapping table to map the previouslywritten physical block to the new physical block address.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 48 through 54 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to handling of write fault errors encountered in a dynamicallymapped storage device. Numerous equivalent methods and techniques willbe readily apparent to those of ordinary skill in the art to implementsuch features as a matter of design choice.

On-The-Fly Head Depopulation

If a subsection of a storage device (e.g., a head or surface) fails, thedata stored in the subsection is typically lost. Typically as presentlypracticed when a head is predicted by a disk drive to be failing, thefailing condition can be signaled to the user, but no other action isperformed to protect the user's data on that subsection. Thus, if theuser does not take corrective action, for example by copying the data toanother disk drive, then the data may be lost if the subsectioneventually fails. Because the LBA directly maps to the particularcylinder, head and sector where data should be located, data may not bemigrated onto another surface by present day disk drives.

In accordance with features and aspects hereof, all user data written tothe dynamically mapped storage device is dynamically mapped from theuser supplied logical address space (logical block addresses or LBAs) tothe physical disk block address space (disk block addresses or DBAsblocks of variable, independent size relative to the LBA size). Thus,features and aspects hereof permit on-the-fly head depopulation toprotect customer data in the event of a possible head or surfacefailure. If the disk drive detects a defective or failing head orsurface, data on the surface may be migrated to other physical locations(e.g., a different surface) on the disk drive. The disk drive furtherchanges the mapping table to reflect that the data has been migratedfrom one surface to another surface. Thus, if the head fails, the dataon the surface is protected through migration to a non-failing surface.From the perspective of the attached host, the data is still availablein the same manner as before the head failure. While the disk drive mayoperate with a diminished capacity due to the unavailability of asurface, a loss of the data has been avoided.

FIG. 59 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to perform on-the-fly headdepopulation. As noted above, disk controller 106 may include indirectlogical to physical mapping element 108 generally responsible fordynamic mapping features of the storage device. An aspect of the logicalto physical mapping element 108 may include head depopulation element5900 operable to perform on-the-fly head depopulation. Head depopulationelement 5900 may include various elements to aid in the protection ofdata on a failing surface detected by head operating parameters analyzerelement 5904. Head operating parameters analyzer element 5904 maymonitor the operating parameters of a head or read/write channel todetect potential reliability issues in the operation of the head, aswell as determining whether the head and/or read/write channel arefailing. For example, head operating temperature, bit error rates fromreading of data, shock and vibration event statistics, etc. may all beused by head operating parameters analyzer element 5904 to detect apossibly failing head. The parameters may also be indicative of afailure of the recording surface associated with the head. In furthersensing a falling surface, head or read/write channel, features andaspects hereof may act to migrate information to another head(surface/channel). Head migration element 5902 processes the migrationof data from a failing head, channel or surface to another surface inthe event of a possible head failure. Migration may include re-writingor re-mapping logical blocks from the failing surface to anothersurface. As used herein, failure of a head, channel or surface areconsidered synonymous with respect to head depopulation actions.

In some instances, it may not be possible to migrate all of the datafrom a failing surface to another surface. For instance, the othersurface may not have sufficient capacity to hold the data stored on thefailing surface. Head depopulation element 5900 may include capacityanalyzer element 5906 for analyzing the current capacity of the diskdrive and the individual recordable surfaces of the disk drive. Thus,capacity analyzer element 5906 may determine that sufficient capacitydoes not exist on another surface to migrate all of the data stored onthe failing surface. Prioritization analyzer element 5908 may prioritizethe migration of data from the failing surface onto another surface toensure that critical data, such as system files, are migrated beforeother data. For example, prioritization analyzer element 5908 may selectblocks deemed to be critical such as file directory and FAT tablestructures stored as user data on the dynamically mapped storage device.Or, for example, data that is observed to be frequently accessed may beselected for prioritization as critical data based on its frequency ofaccess. Other less critical data may have a lower prioritization and bemigrated after critical data. Numerous other heuristic rules will bereadily apparent to those of ordinary skill in the art to identifycritical data that may be prioritized by prioritization analyzer element5908 in accordance with features and aspects hereof.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 5900 through 5908 shown as operable withinthe indirect logical to physical mapping element 108 of disk controller106 may be combined into fewer discrete elements or may be broken upinto a larger number of discrete functional elements as a matter ofdesign choice. Thus, the particular functional decomposition suggestedby FIG. 59 is intended merely as exemplary of one possible functionaldecomposition of elements within disk controller 106.

FIG. 61 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for performingon-the-fly head depopulation. In particular, FIG. 61 broadly representsa method operable within the storage controller in accordance withfeatures and aspects hereof to migrate a logical block from a failinghead surface to another surface. Element 6102 represents disk controller106 detecting a possible head failure. For instance, disk controller 106may detect that the read head continually returns read errors whileprocessing read requests. Those of ordinary skill in the art willrecognize a variety of factors that may be used to detect a possiblehead failure.

Element 6104 represents the disk controller 106 determining whether theread head is failing. A variety of causes may trigger errors on the readhead, and the disk controller 106 may determine whether the read head isactually failing. If the head is not failing, then normal operations ofthe disk drive may be continued in element 6110.

If disk controller 106 determines that the surface is failing, then thedisk controller migrates a logical block from the first surface (e.g.,failing surface) to a second surface (e.g., non-failing surface) inelement 6106. For instance, a logical block may be migrated from a firstphysical block address on the first surface to a second physical blockaddress on a second surface. FIG. 60 is a schematic diagram of anexemplary disk drive including multiple recording surfaces. Firstsurface 6000 (e.g., the failing surface) comprises a logical blockstored in a first physical block address 6004. Element 6106 migrates thelogical block to a second surface 6002, and stores the logical block ata second physical block address 6006 of the second surface. Those ofordinary skill in the art will recognize that read/write head assembliesare often shared between two adjacent surfaces. Thus, a failing head mayrequire migration of data from both surfaces sharing the read/write headassembly.

All of the data on the first surface may be migrated to the secondsurface at once, or the disk controller 106 may migrate the data duringspare or idle processing cycles of the disk drive. “Idle” periods orcycles of the disk controller may be defined as periods in which no reador write request is being processed or is pending, or more broadly,periods during which no host requested operations are currently inprocess or pending. Thus, the attached host may not notice a significantperformance drop of the disk drive during the migration process.

Element 6108 represents disk controller 106 adjusting the mapping tableof the disk drive to map the logical block at the second physical blockaddress of the second surface. Thereafter, if the attached host requeststhe logical block using the LBA, then the disk drive will access thelogical block from the second physical block address. The methodillustrated in FIG. 61 may be repeated to migrate a selected portion orall of the logical blocks stored on the failing head or surface.

FIG. 63 is a flowchart providing exemplary additional details of theprocessing of one embodiment of element 6106 of FIG. 61. As noted above,element 6106 is generally operable to migrate the logical block to asecond physical block address on a second surface of the recordablemedia. Element 6302 represents reading the logical block from the firstphysical block address. Element 6304 represents disk controller 106determining whether sufficient capacity exists on the second surface tomigrate the logical block to the second surface. If sufficient capacitydoes not exist on the second surface to migrate the logical block, thennormal operations of the disk drive continue at element 6308. Ifsufficient capacity exists on the second surface to migrate the logicalblock, then the logical block is re-written at the second physical blockaddress in element 6306.

FIG. 62 is a flowchart providing exemplary additional details of theprocessing of another embodiment of element 6106 of FIG. 61. As notedabove, element 6106 is generally operable to migrate the suppliedlogical block to a second physical block address. Element 6202represents appending the logical block to a buffer to be written to therecordable media. As discussed previously with respect to FIGS. 55-58,the dynamically mapped storage device may store pending write requeststhat may be written to sequential physical blocks in the order in whichdata is stored in the buffer. Additional details regarding the operationof the buffer are provided above in the discussion of FIGS. 55-58.Element 6204 represents writing the buffer to the recordable media inthe order in which the data in stored in the buffer. Thus, the suppliedlogical block is re-written at the second physical block addressresponsive to reaching a position in the buffer of the supplied logicalblock.

FIG. 64 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for performingon-the-fly head depopulation. In particular, FIG. 64 broadly representsa method operable within the storage controller in accordance withfeatures and aspects hereof to provide processing of a subsequent writerequest received after the detection of a possible head failure. Afterdata is migrated from the possible failing surface, it may be beneficialto prevent writing data to the possible failing surface. The disk drivemay continue accepting data storage commands from the attached host aslong as there is storage capacity remaining in good subsections.

Element 6402 represents disk controller 106 determining a remainingcapacity of the recordable media. The remaining capacity may exclude acapacity of the first surface, as any data placed on the first surfacemay be at risk. This may depend on a probability that the first surfacehead may fail.

Element 6404 represents disk controller 106 determining whether there issufficient capacity to store the data on the recordable media. If thereis not sufficient capacity to store the data on the recordable media,then the write is prevented in element 6410. If sufficient capacityexists on the second surface, then the data is written to the secondsurface in element 6408, and the write request is complete.

If sufficient capacity does not exist on the second surface to store thedata, then disk controller 106 may determine whether the first surfaceis reliable enough to store the data in element 6412. If the disk driveis near capacity, it may become necessary to store data on the possiblyfailing surface. When disk controller 106 is faced with an alternativeof placing the data on a possibly failing surface or rejecting thestorage of the data, it may be more beneficial to store the data at riskrather than rejecting the write request.

If disk controller 106 determines that the first surface is reliableenough to store the data on the first surface, then the data may bewritten to the first surface in element 6414, and the write request iscomplete. Otherwise, the write may be prevented in element 6410. Forexample, if the head on the first surface has failed, and the onlyremaining capacity is on the first surface, then the write may beprevented.

The method illustrated in FIG. 64 may be used to preferentially keepdata off the weakest subsections identified at the time of manufacture.Thus, the weakest subsections may not be used until needed for providingfull capacity of the dynamically mapped storage device. If a weaksubsection is identified with a possible failing head, then a logicalblock may be written to other surfaces until the capacity of the weaksubsection is needed. If a logical block is written on the weaksubsection, and capacity subsequently becomes available on anothersurface, then a logical block may be migrated from the weak subsectionto another surface.

FIG. 65 is a flowchart representing another exemplary method operablewithin a storage device controller (e.g., disk controller) inconjunction with the mapping features and aspects discussed herein abovefor performing on-the-fly head depopulation. In particular, FIG. 65broadly represents a method operable within the storage controller inaccordance with features and aspects hereof to provide prioritizing themigration of a plurality of logical blocks from a first surface to asecond surface in the event that the second surface does not containsufficient capacity to store the plurality of logical blocks. Element6502 represents disk controller 106 determining whether the head isfailing. A variety of causes may trigger errors of the read head, anddisk controller 106 may determine whether the head is failing. If thehead is not failing, then normal operations of the disk drive continuein element 6512.

If disk controller 106 determines that the head is failing, then diskcontroller 106 further determines whether sufficient capacity exists ona second surface to hold a plurality of logical blocks stored on thefirst surface in element 6506. If sufficient capacity does not exist tohold the plurality of logical blocks stored on the first surface, thendisk controller 106 may migrate a portion of the plurality of logicalblocks from the first surface to the second surface in element 6514.Element 6516 represents disk controller 106 adjusting the mapping tableto map the migrated logical blocks to LBAs of the second surface. Normaloperations of the disk drive then continue in element 6512.

If sufficient capacity exists on the second surface to hold theplurality of logical blocks stored on the first surface, then diskcontroller 106 may migrate the plurality of logical blocks from thefirst surface to the second surface in element 6508. Element 6510represents-disk controller 106 adjusting the mapping table to map themigrated logical blocks to a plurality of physical block addresses ofthe second surface. Normal operations of the disk drive are thencontinued in element 6512.

FIG. 66 is a flowchart providing exemplary additional details of theprocessing of element 6508 of FIG. 65. As noted above, element 6508 isgenerally operable to migrate the supplied logical block to a secondphysical block address. Element 6602 disk controller 106 prioritizing anorder of migration of the plurality of logical blocks. For instance, theorder of migration may be based on a frequency of access of theplurality of logical blocks, where the most frequently accessed logicalblocks are migrated first. Alternatively, the order of migration may bebased on logical blocks storing selected system files. The selectedsystem files may be for example critical system files. Element 6604represents disk controller 106 migrating the plurality of logical blocksfrom the first surface to the second surface in the order of migration.The disk drive may migrate the most valuable data first, so that if thehead fails during the migration process, then the most valuable data maybe preserved.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 61 through 66 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to provide on-the-fly head depopulation in a dynamically mappedstorage device. Numerous equivalent methods and techniques will bereadily apparent to those of ordinary skill in the art to implement suchfeatures as a matter of design choice.

Thermal Lead-In Writes

Typically in disk drives, the write head needs to warm up and becomestable in flying height prior to writing valid data. If the write headis not stable in flying height prior to writing valid data, then thermalflux may cause data to be unreliable. The write head may warm-up as datais written, but the data initially written to the recordable media asthe write head warms-up may not be reliable. Pre-heaters are now used toassure stability of the head prior to a write operation to avoid thermalinstability of initially written data (e.g., the first block written).However, these pre-heaters add cost and complexity to the disk drive.

In accordance with features and aspects hereof, all user data written tothe dynamically mapped storage device is dynamically mapped from theuser supplied logical address space (logical block addresses or LBAs) tothe physical disk block address space (disk block addresses or DBAsblocks of variable, independent size relative to the LBA size). Thus,features and aspects hereof permit the writing of any size thermallead-in sequence of data to allow the write head to stabilize prior towriting user supplied data. Thus, the write head may begin writing thethermal lead-in sequence of data while warming up. As the write headproceeds to write the thermal lead-in sequence of data, the temperature,flying height, etc. of the write head may stabilize. Once the desiredstability is reached, the write head may begin writing user supplieddata. The dynamically mapped structure allows the write head to beginwriting the thermal lead-in sequence at an available physical block onthe recordable media without overwriting valuable user supplied data.The thermal lead-in sequence may typically comprise data that may be ofno use to the storage device or attached host beyond allowing the writehead to warm-up. Thus, the thermal lead-in sequence data may be removedfrom the recordable media during defragmentation.

FIG. 67 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to provide writing thermal lead-insequences to allow a write head to stabilize prior to writing usersupplied data to a recordable media. As noted above, disk controller 106may include indirect logical to physical mapping element 108 generallyresponsible for dynamic mapping features of the storage device. Anaspect of the logical to physical mapping element 108 may include writehead stability control element 6700 operable to write thermal lead-insequences to allow a write head to stabilize (e.g., reach thermalstability and an associated stabilized flying height) prior to writinguser supplied data to a recordable media. Write head stability controlelement 6700 may include various elements to aid the processing of writerequests by write head control element 6702. Write head control element6702 may process write requests to store data on the recordable media.Write head control element 6702 may further determine whether the writehead is stable prior to beginning the writing process. If the write headis not stable (e.g., not at thermal stability), then write head controlelement 6702 may operate to write a thermal lead-in sequence to allowthe write head to stabilize before writing the user supplied data (e.g.,supplied logical block) to the recordable media.

The thermal lead-in sequences may consume valuable space on therecordable media. As the capacity of the recordable media decreases, itmay become necessary to eliminate the thermal lead-in sequences. Writehead stability control element 6700 may include capacity analyzerelement 6706 for analyzing the current capacity ratio as defined above.As the current capacity ratio increases, less space may be available forstoring or preserving the thermal lead-in sequences. Thus, capacityanalyzer element 6706 may continually monitor the current capacity ratioto determine when the use of thermal lead-in sequences prior to writinguser supplied data may be eliminated, as well as defragmenting the diskdrive to eliminate previously written thermal lead-in sequences.Re-write/re-map processor element 6704 may re-map and re-write (e.g.,migrate) user supplied data to defragment the disk drive and eliminatethe thermal lead-in sequences to provide free space on the recordablemedia for subsequent write requests. The indirect mapping and variablesize data block features and aspects hereof enable such defragmentationand compaction while the indirect mapping allows relocation of physicalstorage space to be performed transparently with respect to host systemsand devices.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 6700 through 6706 shown as operable withinthe indirect logical to physical mapping element 108 of disk controller106 may be combined into fewer discrete elements or may be broken upinto a larger number of discrete functional elements as a matter ofdesign choice. Thus, the particular functional decomposition suggestedby FIG. 67 is intended merely as exemplary of one possible functionaldecomposition of elements within disk controller 106.

FIG. 68 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller 106 of FIG. 1) inconjunction with the mapping features and aspects discussed herein abovefor writing thermal lead-in sequences for allowing the write head tostabilize. In particular, FIG. 68 broadly represents a method operablewithin disk controller 106 in accordance with features and aspectshereof to provide writing thermal lead-in sequences to allow a writehead to stabilize prior to writing user supplied data to recordablemedia. Element 6802 represents the disk controller receiving a requestto write a supplied logical block. For instance, the supplied logicalblock may be provided by an attached host.

Element 6804 represents disk controller 106 positioning the write headon the recordable media in response to receiving the write request. Ifthe write head is not stable, then a thermal lead-in sequence may bewritten to allow the write head to reach a desired stability point.

Element 6806 represents the write head writing a thermal lead-insequence to the recordable media at a first physical block address toallow the write head to stabilize. The stabilization of the write headmay include reaching a thermal stability or stabilized flying height.The length of the thermal lead-in sequence may be selected to adequatelyallow the write head to warm up and stabilize. For instance, the lengthof the thermal lead-in sequence may vary and be selected based on amountof idle time of the write head. Alternatively, the length of the thermallead-in sequence may be fixed as the maximum time needed to ensure thatthe write head has warmed up. Those of ordinary skill in the art willrecognize a variety of factors that may be used to select the length ofthe thermal lead-in sequence to allow the write head to adequatelystabilize prior to writing user supplied data.

Element 6808 represents the write head writing the supplied logicalblock to the recordable media following the thermal lead-in sequence.

Following the completion of element 6806, a mapping table of thedynamically mapped storage device may be adjusted to map the suppliedlogical block at the first physical block address. Those of ordinaryskill in the art will recognize that a dynamically mapped disk drive maywrite more than one supplied logical block during the writing process.As discussed above, a plurality of write requests may be cached andwritten together in a write band (e.g., a buffer as discussed above).Thus for example, a thermal lead-in sequence may be written inconjunction with a first physical block address of the recordable media.A plurality of supplied logical blocks may then be written to therecordable media at a plurality of physical block addresses of therecordable media starting at a second physical block address of therecordable media following the first physical block address. A mappingtable may then be adjusted to map the plurality of supplied logicalblocks at the plurality of physical block addresses.

FIG. 72 represents an exemplary data block or sector recorded using athermal lead-in sequence write. Thermal lead-in sequence 7200 is writtento allow the write head to warm-up. After the write head is stabilized,a preamble sequence 7202 may be written. The preamble sequencerepresents the beginning of valid data in the data block. As discussedabove in reference to FIGS. 15 and 16, a data block or sector maycomprise a preamble sequence 7200 that provides a header portion forinformation regarding the particular disk block, such as a block numberand other metadata information. The sync field 7204 provides a standardbit pattern to allow the read/write channel phase lock loop controls tosynchronize on the upcoming supplied logical block 7206. Following thesupplied logical block 7206 is an error correction code field 7208 toprovide error correcting bits for detecting and correcting various biterrors encountered in reading the supplied logical block 7206 from therecordable media. Those of ordinary skill in art will readily recognizethat the scale of elements in FIG. 72 is not intended to preciselyreflect the relative sizes of the components of a data block written tothe recordable media according to features and aspects hereof Rather,FIG. 72 is intended merely to suggest the typical components of anexemplary data block written to the recordable using a thermal lead-inwrite sequence to allow the write head to stabilize according tofeatures and aspects hereof.

As discussed above, thermal lead-in sequences may consume valuable spaceon the recordable media, and may further cause fragmentation of therecordable media. As discussed above, the dynamically mapped storagedevice may provide sequential writing of concentric cylinders as writerequests are received from an attached host, and may then re-map anddefragment the recordable media at a later time. Thus, supplied logicalblocks may be re-mapped to eliminate the thermal lead-in sequences toprovide space for subsequent write requests. FIGS. 69-71 are flowchartsrepresenting exemplary methods operable within a storage devicecontroller (e.g., disk controller) in conjunction with the mappingfeatures and aspects discussed herein above to provide re-mapping ofphysical blocks to eliminate thermal lead-in sequences.

Element 6902 represents disk controller 106 determining a currentcapacity ratio value indicating a current physical capacity utilizationof the dynamically mapped storage device. Element 6906 represents diskcontroller 106 determining whether the current capacity ratio value hasreached a predefined limit. The predefined limit indicates to thedynamically mapped storage device that non-user supplied data, such asthermal lead-in sequences should be eliminated to free space on therecordable media for additional user supplied data. As discussed above,the predefined limit of the capacity ratio value for example may be 0.5,indicating that the disk drive is near physical capacity, while only 50%of the stored data represents user supplied data. Disk controller 106may continually monitor the current capacity ratio to determine when thepreviously written thermal lead-in sequences may be eliminated. If thecurrent capacity ratio value has not reached the predefined limit, thennormal operations are continued in element 6910. Normal operations mayinclude subsequent read and/or write requests from an attached host,etc.

If the current capacity ratio value has reached the predefined limit,then supplied logical blocks are migrated to a second physical blockaddress of the recordable media in element 6906 to eliminate thermallead-in sequences and de-fragment the recordable media. Element 6908represents disk controller 106 adjusting the mapping table to map thesupplied logical block at the second physical block address. Responsiveto completing element 6908, the disk controller continues normaloperations in element 6910.

FIG. 70 is a flowchart providing exemplary additional details of theprocessing of element 6906 of FIG. 69. As noted above, element 6906 isgenerally operable to migrate the supplied logical block to a secondphysical block address. Element 7002 represents reading the suppliedlogical block from the first physical block address. Element 7004represents adding the supplied logical block to a buffer. As discussedpreviously with respect to FIGS. 55-58, the dynamically mapped storagedevice may store pending write requests in a buffer to be completed at alater time. Additional details regarding the operation of the buffer areprovided above in the discussion of FIGS. 55-58. The buffer may store aplurality of write requests that may be written to a sequential sequenceof physical blocks in the order in which the data is stored in thebuffer. Element 7006 represents writing the buffer to the recordablemedia in the order in which the data is stored in the buffer. Thus, thesupplied logical block is re-written at the second physical blockaddresses responsive to reaching a position in the buffer of thesupplied logical block.

FIG. 71 is a flowchart providing exemplary additional details of theprocessing of element 6906 of FIG. 69. As noted above, element 6906 isgenerally operable to migrate the supplied logical block to a secondphysical block address. Element 7102 represents writing the suppliedlogical block at a second physical address of the recordable media.Element 7104 represents adjusting a mapping table to map the suppliedlogical block at the second physical block address. Thus, the mappingtable will reflect that the supplied logical block is presently locatedat the second physical block address.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 68 through 71 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to provide writing of thermal lead-in sequences in a dynamicallymapped storage device to allow the write head to stabilize prior towriting valid data. Numerous equivalent methods and techniques will bereadily apparent to those of ordinary skill in the art to implement suchfeatures as a matter of design choice.

Handling of Grown Defects

A grown defect occurs on a disk drive when a portion of the recordablemedia does not function properly. Grown defects occur during the use ofthe disk drive, as opposed to other types of disk defects which are theresult of defects detected in the manufacturing process at time ofmanufacture. Any number of factors may cause a grown defect, such asscratches on the recordable media, problems with magnetizing therecordable media, etc.

In accordance with features and aspects hereof, all user data written tothe dynamically mapped storage device is dynamically mapped from theuser supplied logical address space (logical block addresses or LBAs) tothe physical disk block address space (disk block addresses or DBAsblocks of variable, independent size relative to the LBA size). Thus,features and aspects hereof permit handling of grown defects in adynamically mapped storage device without performance losses of one ormore revolutions of the dynamically mapped storage device. If the diskdrive detects a read error during the reading of a logical block, thenthe disk drive does not stop the reading process to handle the readerror as presently practiced. Rather, in accordance with features andaspects hereof, the logical block may be moved to any free location onthe recordable media and remapped accordingly to reflect the newposition. The re-vectored logical block may be buffered for laterwriting to the recordable media.

FIG. 73 is a block diagram providing additional exemplary details of adisk controller as in FIG. 1 enhanced to handle a grown defectencountered during a read operation. The read operation may occurresponsive to a request for access to a logical block by an attachedhost, may occur in response to a verification reading of a writtenblock, or may occur during other processes executed by the diskcontroller. As noted above, disk controller 106 may include indirectlogical to physical mapping element 108 generally responsible fordynamic mapping features of the storage device. An aspect of the logicalto physical mapping element 108 as noted above may include read faultdetection and correction element 7302 operable to handle read errors andgrown defects on the recordable media. Read fault detection andcorrection element 7302 may include various elements to aid in thecorrection of read errors detected by read error detection 7306. Readerror detection element 7306 may monitor the read operations of aread/write head to determine whether a read error has occurred. If aread error is detected, re-write/re-map processor element 7304 mayre-map and re-write the logical block at a different location on therecordable media.

Those of ordinary skill in the art will readily recognize that thevarious functional elements 7300 through 7306 shown as operable withinthe indirect logical to physical mapping element 108 of disk controller106 may be combined into fewer discrete elements or may be broken upinto a larger number of discrete functional elements as a matter ofdesign choice. Thus, the particular functional decomposition suggestedby FIG. 73 is intended merely as exemplary of one possible functionaldecomposition of elements within disk controller 106.

FIG. 74 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for handlinggrown defects encountered in the dynamically mapped storage device. Inparticular, FIG. 74 broadly represents a method operable within the diskcontroller 106 in accordance with features and aspects hereof to handlethe correction of a grown defect encountered during a read error.Element 7402 represents the read head reading a logical block from afirst physical block address of the recordable media.

Element 7404 represents disk controller 106 determining whether a readerror occurred during the reading process as the result of a growndefect. If no read error occurred, then the read operation is complete.

If disk controller 106 determines that a read error occurred as a resultof a grown defect, then the logical block is re-written at a secondphysical block address of the recordable media by disk controller 106responsive to detecting the read error in element 7406. The secondphysical block address may comprise a free physical block anywhere onthe recordable media.

Element 7408 represents disk controller 106 adjusting a mapping table tomap the supplied logical block at the second physical block address. Thelogical block is mapped at the second physical block address like anyother logical block on the recordable media. Thereafter, if the attachedhost requests the logical block, the disk drive may access the logicalblock from the second physical block address. The disk drive may furtherrecord that the first physical block address contains a grown defect,and may not be used in the future.

FIG. 75 is a flowchart providing exemplary additional details of theprocessing of element 7406 of FIG. 74. As noted above, element 7406 isgenerally operable to re-write the logical block to a second physicalblock address of the recordable media. Element 7502 represents appendingthe logical block to a buffer to be written to the recordable media. Asdiscussed previously with respect to FIGS. 55-58, the dynamically mappedstorage device may store pending write requests in a buffer to becompleted at a later time. Additional details regarding the operation ofthe buffer are provided above in the discussion of FIGS. 55-58. Thebuffer may store a plurality of write requests that may be written to asequential sequence of physical blocks in the order in which the data isstored in the buffer. Element 7504 represents writing the buffer to therecordable media in the order in which the data is stored in the buffer.Thus, the logical block is re-written at the second physical blockaddresses responsive to reaching a position in the buffer of thesupplied logical block.

FIG. 76 is a flowchart providing exemplary additional details of theprocessing of element 7406 of FIG. 74. As noted above, element 7406 isgenerally operable to re-write the logical block to a second physicalblock address of the recordable media. Element 7602 represents addingthe logical block to a buffer to be written to the recordable media.Element 7604 represents the disk controller 106 reading a remainingsequential order of logical blocks requested by an attached host.Element 7406 represents disk controller 106 writing the buffer to therecordable media in the order in which the data is stored in the buffer.The logical block is re-written at the second physical block addressresponsive to reaching a position in the buffer of the supplied logicalblock. Thus, the re-write of the logical block at the second physicalblock address may occur subsequent to the completion of a read processcurrently executed by disk controller 106.

FIG. 77 is a flowchart representing an exemplary method operable withina storage device controller (e.g., disk controller) in conjunction withthe mapping features and aspects discussed herein above for handlinggrown defects encountered in the dynamically mapped storage device. Inparticular, FIG. 77 broadly represents a method operable within diskcontroller 106 in accordance with features and aspects hereof to handlethe correction of a grown defect encountered during a read error.Element 7402 represents the disk controller reading a plurality oflogical blocks from the recordable media.

Element 7704 represents disk controller 106 determining whether a readerror occurred during the reading of a logical block from a firstphysical block address of the recordable media as the result of a growndefect. If no read error occurred during the reading process of theplurality of logical blocks, then the read request is complete.

If disk controller 106 determines that a read error occurred as a resultof a grown defect, then the logical block may need to be re-vectored ata second physical block address of the recordable media. However, there-vector of the logical block may be executed after the read request iscompleted. For instance, the logical block may be added to a buffer asdescribed in FIG. 74 to be re-written to the recordable media responsiveto completing the reading process. Element 7706 represents diskcontroller 106 completing reading of the plurality of logical blocksfrom the recordable media. Depending on the size of the grown defect,subsequent errors may be detected by element 7704 during the executionof element 7706.

Element 7708 represents disk controller 106 re-writing the logical blockat a second physical block address of recordable media responsive tocompleting the reading of the plurality of logical blocks.

Element 7710 represents disk controller 106 adjusting a mapping table tomap the supplied logical block at the second physical block address. Ifmultiple errors are encountered while element 7702 operates to read theplurality of logical blocks, then multiple logical blocks may need to bere-vectored by disk controller 106. In this instance, the logical blockscontained in grown defect error areas may be buffered, and elements 7708and 7710 may operate to re-vector each logical block once the readrequest is completed. Disk controller 106 for example may re-write eachlogical block that needs to be re-vectored in a sequential order on thedisk drive in a contiguous sequence of free space.

Those of ordinary skill in the art will readily recognize that themethods of FIGS. 74 through 77 are intended merely as exemplary ofpossible embodiments of methods in accordance with features and aspectshereof to provide handling of grown defect errors in a dynamicallymapped storage device. Numerous equivalent methods and techniques willbe readily apparent to those of ordinary skill in the art to implementsuch features as a matter of design choice.

While the invention has been illustrated and described in the drawingsand foregoing description, such illustration and description is to beconsidered as exemplary and not restrictive in character. One embodimentof the invention and minor variants thereof have been shown anddescribed. Protection is desired for all changes and modifications thatcome within the spirit of the invention. Those skilled in the art willappreciate variations of the above described embodiments that fallwithin the scope of the invention. As a result, the invention is notlimited to the specific examples and illustrations discussed above, butonly by the following claims and their equivalents.

1. A method operable in association with a dynamically mapped storagedevice, the method comprising: detecting an off-track position errorcondition while writing a supplied logical block at a first physicalblock address of a recordable media of the dynamically mapped storagedevice; re-writing the supplied logical block at a second physical blockaddress of the recordable media responsive to detecting the off-trackposition error; and adjusting a mapping table of the dynamically mappedstorage device to map the supplied logical block at the second physicalblock address.
 2. The method of claim 1 wherein the step of detectingthe off-track position error further comprises: determining whether theoff-track position error exceeds a threshold value indicating that datastored in the first physical block address is unreliable.
 3. The methodof claim 1 wherein the step of re-writing the supplied logical blockfurther comprises: adding the supplied logical block to a bufferincluding data that is to be written to the recordable media responsiveto detecting the off-track position error, wherein the data in thebuffer is stored in an order to be written to the recordable media; andwriting the buffer to the recordable media in the order in which thedata is stored in the buffer, wherein the supplied logical block isre-written at the second physical block address responsive to reaching aposition in the buffer of the supplied logical block.
 4. The method ofclaim 3 wherein the step of adding the supplied logical block to thebuffer of further comprises: appending the supplied logical block to thebuffer.
 5. The method of claim 1 further comprising: detectingencroachment of a previously written physical block by writing of thefirst physical block address during the off-track position error,wherein the previously written physical block is associated with alogical block address in the mapping table; retrieving the previouslywritten physical block from a buffer including data that is to bewritten to the recordable media, wherein the buffer stores the mostrecently written physical blocks; re-writing the previously writtenphysical block at a new physical block address of the recordable media;and adjusting the mapping table to map the logical block address to thenew physical block address.
 6. The method of claim 5 wherein the step ofdetecting encroachment further comprises: determining whether theoff-track position error exceeds a threshold value indicating that datastored in the previously written physical block is unreliable.
 7. Themethod of claim 5 wherein the step of re-writing the previously writtenphysical block further comprises: changing a position in the buffer ofthe previously written physical block responsive to detecting theoff-track position error, wherein the data in the buffer is stored in anorder to be written to the recordable media; and writing the buffer tothe recordable media in the order in which the data is stored in thebuffer, wherein the previously written physical block is re-written atthe second physical block address responsive to reaching the position inthe buffer of the previously written physical block.
 8. The method ofclaim 7 wherein the step of writing the buffer further comprises:appending the previously written physical block to the buffer.
 9. Themethod of claim 5 further comprising: reading a plurality of the recentpreviously written physical blocks from the recordable media into thebuffer in response to a reset of the dynamically mapped storage device,wherein the recent previously written physical blocks are used torecover from an off-track position error.
 10. A method operable inassociation with a dynamically mapped storage device, the methodcomprising: receiving a supplied logical block to be written to arecordable media of the dynamically mapped storage device; adding thesupplied logical block to a buffer including data to be written to therecordable media; writing the supplied logical block at a first physicalblock address of the recordable media; detecting an off-track positionerror condition while writing a supplied logical block; and recoveringfrom the off-track position error and re-writing the supplied logicalblock at a second physical block address of the recordable media. 11.The method of claim 10 wherein the recovering step further comprises:changing a position in the buffer of the supplied logical blockresponsive to detecting the off-track position error, wherein the datain the buffer is stored in an order to be written to the recordablemedia; writing the data in the buffer to the recordable media startingat a next position of the buffer; re-writing the supplied logical blockat a second physical block address of the recordable media responsive toreaching the position in the buffer of the supplied logical block; andadjusting a mapping table of the dynamically mapped storage device tomap the supplied logical block at the second physical block address. 12.The method of claim 10 further comprising: sensing a direction of theoff-track position error; determining whether the off-track positionerror exceeds a first threshold value indicating that data stored in thefirst physical block address is unreliable; determining whether theoff-track position error exceeds a second threshold value indicatingthat data stored in the previously written physical block is unreliableif the off-track position error is in the direction of the previouslywritten physical block; changing a position in the buffer of thepreviously written physical block responsive to detecting the off-trackposition error if the off-track position error exceeds the secondthreshold value, wherein the data in the buffer is stored in an order tobe written to the recordable media, and wherein the previously writtenphysical block is associated with a logical block address in the mappingtable; writing the buffer to the recordable media in the order in whichthe data is stored in the buffer, wherein the previously writtenphysical block is re-written at the second physical block addressresponsive to reaching the position in the buffer of the previouslywritten physical block; adjusting the mapping table to map the logicalblock address to the new physical block address.
 13. A dynamicallymapped storage device adapted to receive a request from an attached hostfor access to a logical block identified by a logical block address, thedynamically mapped storage device comprising: a recordable mediacomprising a plurality of physical disk blocks identified by acorresponding physical disk block address; and a disk controller adaptedto detect an off-track position error condition while writing a suppliedlogical block at a first physical block address of the recordable media,and further adapted to re-write the supplied logical block at a secondphysical block address of the recordable media responsive to detectingthe off-track position error; and further adapted to adjust the mappingtable to map the supplied logical block at the second physical blockaddress.
 14. The dynamically mapped storage device of claim 13 whereinthe disk controller is further adapted to determine whether theoff-track position error exceeds a threshold value indicating that datastored in the first physical block address is unreliable.
 15. Thedynamically mapped storage device of claim 13 wherein the diskcontroller is further adapted: to add the supplied logical block to abuffer including data that is to be written to the recordable mediaresponsive to detecting the off-track position error, wherein the datain the buffer is stored in an order to be written to the recordablemedia; and to write the buffer to the recordable media in the order inwhich the data is stored in the buffer, wherein the supplied logicalblock is re-written at the second physical block address responsive toreaching a position in the buffer of the supplied logical block.
 16. Thedynamically mapped storage device of claim 15 wherein the diskcontroller is further adapted to append the supplied logical block tothe buffer.
 17. The dynamically mapped storage device of claim 13wherein the disk controller is further adapted: to detect encroachmentof a previously written physical block by writing of the first physicalblock address during the off-track position error, wherein thepreviously written physical block is associated with a logical blockaddress in the mapping table; to retrieve the previously writtenphysical block from a buffer including data that is to be written to therecordable media, wherein the buffer stores the most recently writtenphysical blocks; to re-write the previously written physical block at anew physical block address of the recordable media; and to adjust themapping table to map the logical block address to the new physical blockaddress.
 18. The dynamically mapped storage device of claim 17 whereinthe disk controller is further adapted to determine whether theoff-track position error exceeds a threshold value indicating that datastored in the previously written physical block is unreliable.
 19. Thedynamically mapped storage device of claim 17 wherein the diskcontroller is further adapted: to change a position in the buffer of thepreviously written physical block responsive to detecting the off-trackposition error, wherein the data in the buffer is stored in an order tobe written to the recordable media; and to write the buffer to therecordable media in the order in which the data is stored in the buffer,wherein the previously written physical block is re-written at thesecond physical block address responsive to reaching the position in thebuffer of the previously written physical block.
 20. The dynamicallymapped storage device of claim 19 wherein the disk controller is furtheradapted to append the previously written physical block to the buffer.21. The dynamically mapped storage device of claim 17 wherein the diskcontroller is further adapted to read a plurality of the recentpreviously written physical blocks from the recordable media into thebuffer in response to a reset of the dynamically mapped storage device,wherein the recent previously written physical blocks are used torecover from an off-track position error.